DISCOURSE ON THE METHOD
OF RIGHTLY CONDUCTING THE REASON,
AND SEEKING TRUTH IN THE SCIENCES

PREFATORY NOTE BY THE AUTHOR

If this Discourse appear too long to be read at once, it may be divided into
six Parts: and, in the first, will be found various considerations touching the
Sciences; in the second, the principal rules of the Method which the Author has
discovered, in the third, certain of the rules of Morals which he has deduced
from this Method; in the fourth, the reasonings by which he establishes the
existence of God and of the Human Soul, which are the foundations of his
Metaphysic; in the fifth, the order of the Physical questions which he has
investigated, and, in particular, the explication of the motion of the heart
and of some other difficulties pertaining to Medicine, as also the difference
between the soul of man and that of the brutes; and, in the last, what the
Author believes to be required in order to greater advancement in the
investigation of Nature than has yet been made, with the reasons that have
induced him to write.

PART I

Good sense is, of all things among men, the most equally distributed; for every
one thinks himself so abundantly provided with it, that those even who are the
most difficult to satisfy in everything else, do not usually desire a larger
measure of this quality than they already possess. And in this it is not likely
that all are mistaken the conviction is rather to be held as testifying that
the power of judging aright and of distinguishing truth from error, which is
properly what is called good sense or reason, is by nature equal in all men;
and that the diversity of our opinions, consequently, does not arise from some
being endowed with a larger share of reason than others, but solely from this,
that we conduct our thoughts along different ways, and do not fix our attention
on the same objects. For to be possessed of a vigorous mind is not enough; the
prime requisite is rightly to apply it. The greatest minds, as they are capable
of the highest excellences, are open likewise to the greatest aberrations; and
those who travel very slowly may yet make far greater progress, provided they
keep always to the straight road, than those who, while they run, forsake it.

For myself, I have never fancied my mind to be in any respect more perfect than
those of the generality; on the contrary, I have often wished that I were equal
to some others in promptitude of thought, or in clearness and distinctness of
imagination, or in fullness and readiness of memory. And besides these, I know
of no other qualities that contribute to the perfection of the mind; for as to
the reason or sense, inasmuch as it is that alone which constitutes us men, and
distinguishes us from the brutes, I am disposed to believe that it is to be
found complete in each individual; and on this point to adopt the common
opinion of philosophers, who say that the difference of greater and less holds
only among the accidents, and not among the forms or natures of individuals of
the same species.

I will not hesitate, however, to avow my belief that it has been my singular
good fortune to have very early in life fallen in with certain tracks which
have conducted me to considerations and maxims, of which I have formed a method
that gives me the means, as I think, of gradually augmenting my knowledge, and
of raising it by little and little to the highest point which the mediocrity of
my talents and the brief duration of my life will permit me to reach. For I
have already reaped from it such fruits that, although I have been accustomed
to think lowly enough of myself, and although when I look with the eye of a
philosopher at the varied courses and pursuits of mankind at large, I find
scarcely one which does not appear in vain and useless, I nevertheless derive
the highest satisfaction from the progress I conceive myself to have already
made in the search after truth, and cannot help entertaining such expectations
of the future as to believe that if, among the occupations of men as men, there
is any one really excellent and important, it is that which I have chosen.

After all, it is possible I may be mistaken; and it is but a little copper and
glass, perhaps, that I take for gold and diamonds. I know how very liable we
are to delusion in what relates to ourselves, and also how much the judgments
of our friends are to be suspected when given in our favor. But I shall
endeavor in this discourse to describe the paths I have followed, and to
delineate my life as in a picture, in order that each one may also be able to
judge of them for himself, and that in the general opinion entertained of them,
as gathered from current report, I myself may have a new help towards
instruction to be added to those I have been in the habit of employing.

My present design, then, is not to teach the method which each ought to follow
for the right conduct of his reason, but solely to describe the way in which I
have endeavored to conduct my own. They who set themselves to give precepts
must of course regard themselves as possessed of greater skill than those to
whom they prescribe; and if they err in the slightest particular, they subject
themselves to censure. But as this tract is put forth merely as a history, or,
if you will, as a tale, in which, amid some examples worthy of imitation, there
will be found, perhaps, as many more which it were advisable not to follow, I
hope it will prove useful to some without being hurtful to any, and that my
openness will find some favor with all.

From my childhood, I have been familiar with letters; and as I was given to
believe that by their help a clear and certain knowledge of all that is useful
in life might be acquired, I was ardently desirous of instruction. But as soon
as I had finished the entire course of study, at the close of which it is
customary to be admitted into the order of the learned, I completely changed my
opinion. For I found myself involved in so many doubts and errors, that I was
convinced I had advanced no farther in all my attempts at learning, than the
discovery at every turn of my own ignorance. And yet I was studying in one of
the most celebrated schools in Europe, in which I thought there must be learned
men, if such were anywhere to be found. I had been taught all that others
learned there; and not contented with the sciences actually taught us, I had,
in addition, read all the books that had fallen into my hands, treating of such
branches as are esteemed the most curious and rare. I knew the judgment which
others had formed of me; and I did not find that I was considered inferior to
my fellows, although there were among them some who were already marked out to
fill the places of our instructors. And, in fine, our age appeared to me as
flourishing, and as fertile in powerful minds as any preceding one. I was thus
led to take the liberty of judging of all other men by myself, and of
concluding that there was no science in existence that was of such a nature as
I had previously been given to believe.

I still continued, however, to hold in esteem the studies of the schools. I was
aware that the languages taught in them are necessary to the understanding of
the writings of the ancients; that the grace of fable stirs the mind; that the
memorable deeds of history elevate it; and, if read with discretion, aid in
forming the judgment; that the perusal of all excellent books is, as it were,
to interview with the noblest men of past ages, who have written them, and even
a studied interview, in which are discovered to us only their choicest
thoughts; that eloquence has incomparable force and beauty; that poesy has its
ravishing graces and delights; that in the mathematics there are many refined
discoveries eminently suited to gratify the inquisitive, as well as further all
the arts an lessen the labour of man; that numerous highly useful precepts and
exhortations to virtue are contained in treatises on morals; that theology
points out the path to heaven; that philosophy affords the means of discoursing
with an appearance of truth on all matters, and commands the admiration of the
more simple; that jurisprudence, medicine, and the other sciences, secure for
their cultivators honors and riches; and, in fine, that it is useful to bestow
some attention upon all, even upon those abounding the most in superstition and
error, that we may be in a position to determine their real value, and guard
against being deceived.

But I believed that I had already given sufficient time to languages, and
likewise to the reading of the writings of the ancients, to their histories and
fables. For to hold converse with those of other ages and to travel, are almost
the same thing. It is useful to know something of the manners of different
nations, that we may be enabled to form a more correct judgment regarding our
own, and be prevented from thinking that everything contrary to our customs is
ridiculous and irrational, a conclusion usually come to by those whose
experience has been limited to their own country. On the other hand, when too
much time is occupied in traveling, we become strangers to our native country;
and the over curious in the customs of the past are generally ignorant of those
of the present. Besides, fictitious narratives lead us to imagine the
possibility of many events that are impossible; and even the most faithful
histories, if they do not wholly misrepresent matters, or exaggerate their
importance to render the account of them more worthy of perusal, omit, at
least, almost always the meanest and least striking of the attendant
circumstances; hence it happens that the remainder does not represent the
truth, and that such as regulate their conduct by examples drawn from this
source, are apt to fall into the extravagances of the knight-errants of
romance, and to entertain projects that exceed their powers.

I esteemed eloquence highly, and was in raptures with poesy; but I thought that
both were gifts of nature rather than fruits of study. Those in whom the
faculty of reason is predominant, and who most skillfully dispose their
thoughts with a view to render them clear and intelligible, are always the best
able to persuade others of the truth of what they lay down, though they should
speak only in the language of Lower Brittany, and be wholly ignorant of the
rules of rhetoric; and those whose minds are stored with the most agreeable
fancies, and who can give expression to them with the greatest embellishment
and harmony, are still the best poets, though unacquainted with the art of
poetry.

I was especially delighted with the mathematics, on account of the certitude
and evidence of their reasonings; but I had not as yet a precise knowledge of
their true use; and thinking that they but contributed to the advancement of
the mechanical arts, I was astonished that foundations, so strong and solid,
should have had no loftier superstructure reared on them. On the other hand, I
compared the disquisitions of the ancient moralists to very towering and
magnificent palaces with no better foundation than sand and mud: they laud the
virtues very highly, and exhibit them as estimable far above anything on earth;
but they give us no adequate criterion of virtue, and frequently that which
they designate with so fine a name is but apathy, or pride, or despair, or
parricide.

I revered our theology, and aspired as much as any one to reach heaven: but
being given assuredly to understand that the way is not less open to the most
ignorant than to the most learned, and that the revealed truths which lead to
heaven are above our comprehension, I did not presume to subject them to the
impotency of my reason; and I thought that in order competently to undertake
their examination, there was need of some special help from heaven, and of
being more than man.

Of philosophy I will say nothing, except that when I saw that it had been
cultivated for many ages by the most distinguished men, and that yet there is
not a single matter within its sphere which is not still in dispute, and
nothing, therefore, which is above doubt, I did not presume to anticipate that
my success would be greater in it than that of others; and further, when I
considered the number of conflicting opinions touching a single matter that may
be upheld by learned men, while there can be but one true, I reckoned as
well-nigh false all that was only probable.

As to the other sciences, inasmuch as these borrow their principles from
philosophy, I judged that no solid superstructures could be reared on
foundations so infirm; and neither the honor nor the gain held out by them was
sufficient to determine me to their cultivation: for I was not, thank Heaven,
in a condition which compelled me to make merchandise of science for the
bettering of my fortune; and though I might not profess to scorn glory as a
cynic, I yet made very slight account of that honor which I hoped to acquire
only through fictitious titles. And, in fine, of false sciences I thought I
knew the worth sufficiently to escape being deceived by the professions of an
alchemist, the predictions of an astrologer, the impostures of a magician, or
by the artifices and boasting of any of those who profess to know things of
which they are ignorant.

For these reasons, as soon as my age permitted me to pass from under the
control of my instructors, I entirely abandoned the study of letters, and
resolved no longer to seek any other science than the knowledge of myself, or
of the great book of the world. I spent the remainder of my youth in traveling,
in visiting courts and armies, in holding intercourse with men of different
dispositions and ranks, in collecting varied experience, in proving myself in
the different situations into which fortune threw me, and, above all, in making
such reflection on the matter of my experience as to secure my improvement. For
it occurred to me that I should find much more truth in the reasonings of each
individual with reference to the affairs in which he is personally interested,
and the issue of which must presently punish him if he has judged amiss, than
in those conducted by a man of letters in his study, regarding speculative
matters that are of no practical moment, and followed by no consequences to
himself, farther, perhaps, than that they foster his vanity the better the more
remote they are from common sense; requiring, as they must in this case, the
exercise of greater ingenuity and art to render them probable. In addition, I
had always a most earnest desire to know how to distinguish the true from the
false, in order that I might be able clearly to discriminate the right path in
life, and proceed in it with confidence.

It is true that, while busied only in considering the manners of other men, I
found here, too, scarce any ground for settled conviction, and remarked hardly
less contradiction among them than in the opinions of the philosophers. So that
the greatest advantage I derived from the study consisted in this, that,
observing many things which, however extravagant and ridiculous to our
apprehension, are yet by common consent received and approved by other great
nations, I learned to entertain too decided a belief in regard to nothing of
the truth of which I had been persuaded merely by example and custom; and thus
I gradually extricated myself from many errors powerful enough to darken our
natural intelligence, and incapacitate us in great measure from listening to
reason. But after I had been occupied several years in thus studying the book
of the world, and in essaying to gather some experience, I at length resolved
to make myself an object of study, and to employ all the powers of my mind in
choosing the paths I ought to follow, an undertaking which was accompanied with
greater success than it would have been had I never quitted my country or my
books.

PART II

I was then in Germany, attracted thither by the wars in that country, which
have not yet been brought to a termination; and as I was returning to the army
from the coronation of the emperor, the setting in of winter arrested me in a
locality where, as I found no society to interest me, and was besides
fortunately undisturbed by any cares or passions, I remained the whole day in
seclusion, with full opportunity to occupy my attention with my own thoughts.
Of these one of the very first that occurred to me was, that there is seldom so
much perfection in works composed of many separate parts, upon which different
hands had been employed, as in those completed by a single master. Thus it is
observable that the buildings which a single architect has planned and
executed, are generally more elegant and commodious than those which several
have attempted to improve, by making old walls serve for purposes for which
they were not originally built. Thus also, those ancient cities which, from
being at first only villages, have become, in course of time, large towns, are
usually but ill laid out compared with the regularity constructed towns which a
professional architect has freely planned on an open plain; so that although
the several buildings of the former may often equal or surpass in beauty those
of the latter, yet when one observes their indiscriminate juxtaposition, there
a large one and here a small, and the consequent crookedness and irregularity
of the streets, one is disposed to allege that chance rather than any human
will guided by reason must have led to such an arrangement. And if we consider
that nevertheless there have been at all times certain officers whose duty it
was to see that private buildings contributed to public ornament, the
difficulty of reaching high perfection with but the materials of others to
operate on, will be readily acknowledged. In the same way I fancied that those
nations which, starting from a semi-barbarous state and advancing to
civilization by slow degrees, have had their laws successively determined, and,
as it were, forced upon them simply by experience of the hurtfulness of
particular crimes and disputes, would by this process come to be possessed of
less perfect institutions than those which, from the commencement of their
association as communities, have followed the appointments of some wise
legislator. It is thus quite certain that the constitution of the true
religion, the ordinances of which are derived from God, must be incomparably
superior to that of every other. And, to speak of human affairs, I believe that
the pre-eminence of Sparta was due not to the goodness of each of its laws in
particular, for many of these were very strange, and even opposed to good
morals, but to the circumstance that, originated by a single individual, they
all tended to a single end. In the same way I thought that the sciences
contained in books (such of them at least as are made up of probable
reasonings, without demonstrations), composed as they are of the opinions of
many different individuals massed together, are farther removed from truth than
the simple inferences which a man of good sense using his natural and
unprejudiced judgment draws respecting the matters of his experience. And
because we have all to pass through a state of infancy to manhood, and have
been of necessity, for a length of time, governed by our desires and preceptors
(whose dictates were frequently conflicting, while neither perhaps always
counseled us for the best), I farther concluded that it is almost impossible
that our judgments can be so correct or solid as they would have been, had our
reason been mature from the moment of our birth, and had we always been guided
by it alone.

It is true, however, that it is not customary to pull down all the houses of a
town with the single design of rebuilding them differently, and thereby
rendering the streets more handsome; but it often happens that a private
individual takes down his own with the view of erecting it anew, and that
people are even sometimes constrained to this when their houses are in danger
of falling from age, or when the foundations are insecure. With this before me
by way of example, I was persuaded that it would indeed be preposterous for a
private individual to think of reforming a state by fundamentally changing it
throughout, and overturning it in order to set it up amended; and the same I
thought was true of any similar project for reforming the body of the sciences,
or the order of teaching them established in the schools: but as for the
opinions which up to that time I had embraced, I thought that I could not do
better than resolve at once to sweep them wholly away, that I might afterwards
be in a position to admit either others more correct, or even perhaps the same
when they had undergone the scrutiny of reason. I firmly believed that in this
way I should much better succeed in the conduct of my life, than if I built
only upon old foundations, and leaned upon principles which, in my youth, I had
taken upon trust. For although I recognized various difficulties in this
undertaking, these were not, however, without remedy, nor once to be compared
with such as attend the slightest reformation in public affairs. Large bodies,
if once overthrown, are with great difficulty set up again, or even kept erect
when once seriously shaken, and the fall of such is always disastrous. Then if
there are any imperfections in the constitutions of states (and that many such
exist the diversity of constitutions is alone sufficient to assure us), custom
has without doubt materially smoothed their inconveniences, and has even
managed to steer altogether clear of, or insensibly corrected a number which
sagacity could not have provided against with equal effect; and, in fine, the
defects are almost always more tolerable than the change necessary for their
removal; in the same manner that highways which wind among mountains, by being
much frequented, become gradually so smooth and commodious, that it is much
better to follow them than to seek a straighter path by climbing over the tops
of rocks and descending to the bottoms of precipices.

Hence it is that I cannot in any degree approve of those restless and busy
meddlers who, called neither by birth nor fortune to take part in the
management of public affairs, are yet always projecting reforms; and if I
thought that this tract contained aught which might justify the suspicion that
I was a victim of such folly, I would by no means permit its publication. I
have never contemplated anything higher than the reformation of my own
opinions, and basing them on a foundation wholly my own. And although my own
satisfaction with my work has led me to present here a draft of it, I do not by
any means therefore recommend to every one else to make a similar attempt.
Those whom God has endowed with a larger measure of genius will entertain,
perhaps, designs still more exalted; but for the many I am much afraid lest
even the present undertaking be more than they can safely venture to imitate.
The single design to strip one’s self of all past beliefs is one that
ought not to be taken by every one. The majority of men is composed of two
classes, for neither of which would this be at all a befitting resolution: in
the first place, of those who with more than a due confidence in their own
powers, are precipitate in their judgments and want the patience requisite for
orderly and circumspect thinking; whence it happens, that if men of this class
once take the liberty to doubt of their accustomed opinions, and quit the
beaten highway, they will never be able to thread the byway that would lead
them by a shorter course, and will lose themselves and continue to wander for
life; in the second place, of those who, possessed of sufficient sense or
modesty to determine that there are others who excel them in the power of
discriminating between truth and error, and by whom they may be instructed,
ought rather to content themselves with the opinions of such than trust for
more correct to their own reason.

For my own part, I should doubtless have belonged to the latter class, had I
received instruction from but one master, or had I never known the diversities
of opinion that from time immemorial have prevailed among men of the greatest
learning. But I had become aware, even so early as during my college life, that
no opinion, however absurd and incredible, can be imagined, which has not been
maintained by some on of the philosophers; and afterwards in the course of my
travels I remarked that all those whose opinions are decidedly repugnant to
ours are not in that account barbarians and savages, but on the contrary that
many of these nations make an equally good, if not better, use of their reason
than we do. I took into account also the very different character which a
person brought up from infancy in France or Germany exhibits, from that which,
with the same mind originally, this individual would have possessed had he
lived always among the Chinese or with savages, and the circumstance that in
dress itself the fashion which pleased us ten years ago, and which may again,
perhaps, be received into favor before ten years have gone, appears to us at
this moment extravagant and ridiculous. I was thus led to infer that the ground
of our opinions is far more custom and example than any certain knowledge. And,
finally, although such be the ground of our opinions, I remarked that a
plurality of suffrages is no guarantee of truth where it is at all of difficult
discovery, as in such cases it is much more likely that it will be found by one
than by many. I could, however, select from the crowd no one whose opinions
seemed worthy of preference, and thus I found myself constrained, as it were,
to use my own reason in the conduct of my life.

But like one walking alone and in the dark, I resolved to proceed so slowly and
with such circumspection, that if I did not advance far, I would at least guard
against falling. I did not even choose to dismiss summarily any of the opinions
that had crept into my belief without having been introduced by reason, but
first of all took sufficient time carefully to satisfy myself of the general
nature of the task I was setting myself, and ascertain the true method by which
to arrive at the knowledge of whatever lay within the compass of my powers.

Among the branches of philosophy, I had, at an earlier period, given some
attention to logic, and among those of the mathematics to geometrical analysis
and algebra,–three arts or sciences which ought, as I conceived, to contribute
something to my design. But, on examination, I found that, as for logic, its
syllogisms and the majority of its other precepts are of avail–rather in the
communication of what we already know, or even as the art of Lully, in speaking
without judgment of things of which we are ignorant, than in the investigation
of the unknown; and although this science contains indeed a number of correct
and very excellent precepts, there are, nevertheless, so many others, and these
either injurious or superfluous, mingled with the former, that it is almost
quite as difficult to effect a severance of the true from the false as it is to
extract a Diana or a Minerva from a rough block of marble. Then as to the
analysis of the ancients and the algebra of the moderns, besides that they
embrace only matters highly abstract, and, to appearance, of no use, the former
is so exclusively restricted to the consideration of figures, that it can
exercise the understanding only on condition of greatly fatiguing the
imagination; and, in the latter, there is so complete a subjection to certain
rules and formulas, that there results an art full of confusion and obscurity
calculated to embarrass, instead of a science fitted to cultivate the mind. By
these considerations I was induced to seek some other method which would
comprise the advantages of the three and be exempt from their defects. And as a
multitude of laws often only hampers justice, so that a state is best governed
when, with few laws, these are rigidly administered; in like manner, instead of
the great number of precepts of which logic is composed, I believed that the
four following would prove perfectly sufficient for me, provided I took the
firm and unwavering resolution never in a single instance to fail in observing
them.

The first was never to accept anything for true which I did not clearly know to
be such; that is to say, carefully to avoid precipitancy and prejudice, and to
comprise nothing more in my judgement than what was presented to my mind so
clearly and distinctly as to exclude all ground of doubt.

The second, to divide each of the difficulties under examination into as many
parts as possible, and as might be necessary for its adequate solution.

The third, to conduct my thoughts in such order that, by commencing with
objects the simplest and easiest to know, I might ascend by little and little,
and, as it were, step by step, to the knowledge of the more complex; assigning
in thought a certain order even to those objects which in their own nature do
not stand in a relation of antecedence and sequence.

And the last, in every case to make enumerations so complete, and
reviews so general, that I might be assured that nothing was omitted.

The long chains of simple and easy reasonings by means of which geometers are
accustomed to reach the conclusions of their most difficult demonstrations, had
led me to imagine that all things, to the knowledge of which man is competent,
are mutually connected in the same way, and that there is nothing so far
removed from us as to be beyond our reach, or so hidden that we cannot discover
it, provided only we abstain from accepting the false for the true, and always
preserve in our thoughts the order necessary for the deduction of one truth
from another. And I had little difficulty in determining the objects with which
it was necessary to commence, for I was already persuaded that it must be with
the simplest and easiest to know, and, considering that of all those who have
hitherto sought truth in the sciences, the mathematicians alone have been able
to find any demonstrations, that is, any certain and evident reasons, I did not
doubt but that such must have been the rule of their investigations. I resolved
to commence, therefore, with the examination of the simplest objects, not
anticipating, however, from this any other advantage than that to be found in
accustoming my mind to the love and nourishment of truth, and to a distaste for
all such reasonings as were unsound. But I had no intention on that account of
attempting to master all the particular sciences commonly denominated
mathematics: but observing that, however different their objects, they all
agree in considering only the various relations or proportions subsisting among
those objects, I thought it best for my purpose to consider these proportions
in the most general form possible, without referring them to any objects in
particular, except such as would most facilitate the knowledge of them, and
without by any means restricting them to these, that afterwards I might thus be
the better able to apply them to every other class of objects to which they are
legitimately applicable. Perceiving further, that in order to understand these
relations I should sometimes have to consider them one by one and sometimes
only to bear them in mind, or embrace them in the aggregate, I thought that, in
order the better to consider them individually, I should view them as
subsisting between straight lines, than which I could find no objects more
simple, or capable of being more distinctly represented to my imagination and
senses; and on the other hand, that in order to retain them in the memory or
embrace an aggregate of many, I should express them by certain characters the
briefest possible. In this way I believed that I could borrow all that was best
both in geometrical analysis and in algebra, and correct all the defects of the
one by help of the other.

And, in point of fact, the accurate observance of these few precepts gave me, I
take the liberty of saying, such ease in unraveling all the questions embraced
in these two sciences, that in the two or three months I devoted to their
examination, not only did I reach solutions of questions I had formerly deemed
exceedingly difficult but even as regards questions of the solution of which I
continued ignorant, I was enabled, as it appeared to me, to determine the means
whereby, and the extent to which a solution was possible; results attributable
to the circumstance that I commenced with the simplest and most general truths,
and that thus each truth discovered was a rule available in the discovery of
subsequent ones Nor in this perhaps shall I appear too vain, if it be
considered that, as the truth on any particular point is one whoever apprehends
the truth, knows all that on that point can be known. The child, for example,
who has been instructed in the elements of arithmetic, and has made a
particular addition, according to rule, may be assured that he has found, with
respect to the sum of the numbers before him, and that in this instance is
within the reach of human genius. Now, in conclusion, the method which teaches
adherence to the true order, and an exact enumeration of all the conditions of
the thing sought includes all that gives certitude to the rules of arithmetic.

But the chief ground of my satisfaction with thus method, was the assurance I
had of thereby exercising my reason in all matters, if not with absolute
perfection, at least with the greatest attainable by me: besides, I was
conscious that by its use my mind was becoming gradually habituated to clearer
and more distinct conceptions of its objects; and I hoped also, from not having
restricted this method to any particular matter, to apply it to the
difficulties of the other sciences, with not less success than to those of
algebra. I should not, however, on this account have ventured at once on the
examination of all the difficulties of the sciences which presented themselves
to me, for this would have been contrary to the order prescribed in the method,
but observing that the knowledge of such is dependent on principles borrowed
from philosophy, in which I found nothing certain, I thought it necessary first
of all to endeavor to establish its principles. And because I observed,
besides, that an inquiry of this kind was of all others of the greatest moment,
and one in which precipitancy and anticipation in judgment were most to be
dreaded, I thought that I ought not to approach it till I had reached a more
mature age (being at that time but twenty-three), and had first of all employed
much of my time in preparation for the work, as well by eradicating from my
mind all the erroneous opinions I had up to that moment accepted, as by
amassing variety of experience to afford materials for my reasonings, and by
continually exercising myself in my chosen method with a view to increased
skill in its application.

PART III

And finally, as it is not enough, before commencing to rebuild the house in
which we live, that it be pulled down, and materials and builders provided, or
that we engage in the work ourselves, according to a plan which we have
beforehand carefully drawn out, but as it is likewise necessary that we be
furnished with some other house in which we may live commodiously during the
operations, so that I might not remain irresolute in my actions, while my
reason compelled me to suspend my judgement, and that I might not be prevented
from living thenceforward in the greatest possible felicity, I formed a
provisory code of morals, composed of three or four maxims, with which I am
desirous to make you acquainted.

The first was to obey the laws and customs of my country, adhering
firmly to the faith in which, by the grace of God, I had been educated from my
childhood and regulating my conduct in every other matter according to the most
moderate opinions, and the farthest removed from extremes, which should happen
to be adopted in practice with general consent of the most judicious of those
among whom I might be living. For as I had from that time begun to hold my own
opinions for nought because I wished to subject them all to examination, I was
convinced that I could not do better than follow in the meantime the opinions
of the most judicious; and although there are some perhaps among the Persians
and Chinese as judicious as among ourselves, expediency seemed to dictate that
I should regulate my practice conformably to the opinions of those with whom I
should have to live; and it appeared to me that, in order to ascertain the real
opinions of such, I ought rather to take cognizance of what they practised than
of what they said, not only because, in the corruption of our manners, there
are few disposed to speak exactly as they believe, but also because very many
are not aware of what it is that they really believe; for, as the act of mind
by which a thing is believed is different from that by which we know that we
believe it, the one act is often found without the other. Also, amid many
opinions held in equal repute, I chose always the most moderate, as much for
the reason that these are always the most convenient for practice, and probably
the best (for all excess is generally vicious), as that, in the event of my
falling into error, I might be at less distance from the truth than if, having
chosen one of the extremes, it should turn out to be the other which I ought to
have adopted. And I placed in the class of extremes especially all promises by
which somewhat of our freedom is abridged; not that I disapproved of the laws
which, to provide against the instability of men of feeble resolution, when
what is sought to be accomplished is some good, permit engagements by vows and
contracts binding the parties to persevere in it, or even, for the security of
commerce, sanction similar engagements where the purpose sought to be realized
is indifferent: but because I did not find anything on earth which was wholly
superior to change, and because, for myself in particular, I hoped gradually to
perfect my judgments, and not to suffer them to deteriorate, I would have
deemed it a grave sin against good sense, if, for the reason that I approved of
something at a particular time, I therefore bound myself to hold it for good at
a subsequent time, when perhaps it had ceased to be so, or I had ceased to
esteem it such.

My second maxim was to be as firm and resolute in my actions as I was
able, and not to adhere less steadfastly to the most doubtful opinions, when
once adopted, than if they had been highly certain; imitating in this the
example of travelers who, when they have lost their way in a forest, ought not
to wander from side to side, far less remain in one place, but proceed
constantly towards the same side in as straight a line as possible, without
changing their direction for slight reasons, although perhaps it might be
chance alone which at first determined the selection; for in this way, if they
do not exactly reach the point they desire, they will come at least in the end
to some place that will probably be preferable to the middle of a forest. In
the same way, since in action it frequently happens that no delay is
permissible, it is very certain that, when it is not in our power to determine
what is true, we ought to act according to what is most probable; and even
although we should not remark a greater probability in one opinion than in
another, we ought notwithstanding to choose one or the other, and afterwards
consider it, in so far as it relates to practice, as no longer dubious, but
manifestly true and certain, since the reason by which our choice has been
determined is itself possessed of these qualities. This principle was
sufficient thenceforward to rid me of all those repentings and pangs of remorse
that usually disturb the consciences of such feeble and uncertain minds as,
destitute of any clear and determinate principle of choice, allow themselves
one day to adopt a course of action as the best, which they abandon the next,
as the opposite.

My third maxim was to endeavor always to conquer myself rather than
fortune, and change my desires rather than the order of the world, and in
general, accustom myself to the persuasion that, except our own thoughts, there
is nothing absolutely in our power; so that when we have done our best in
things external to us, all wherein we fail of success is to be held, as regards
us, absolutely impossible: and this single principle seemed to me sufficient to
prevent me from desiring for the future anything which I could not obtain, and
thus render me contented; for since our will naturally seeks those objects
alone which the understanding represents as in some way possible of attainment,
it is plain, that if we consider all external goods as equally beyond our
power, we shall no more regret the absence of such goods as seem due to our
birth, when deprived of them without any fault of ours, than our not possessing
the kingdoms of China or Mexico, and thus making, so to speak, a virtue of
necessity, we shall no more desire health in disease, or freedom in
imprisonment, than we now do bodies incorruptible as diamonds, or the wings of
birds to fly with. But I confess there is need of prolonged discipline and
frequently repeated meditation to accustom the mind to view all objects in this
light; and I believe that in this chiefly consisted the secret of the power of
such philosophers as in former times were enabled to rise superior to the
influence of fortune, and, amid suffering and poverty, enjoy a happiness which
their gods might have envied. For, occupied incessantly with the consideration
of the limits prescribed to their power by nature, they became so entirely
convinced that nothing was at their disposal except their own thoughts, that
this conviction was of itself sufficient to prevent their entertaining any
desire of other objects; and over their thoughts they acquired a sway so
absolute, that they had some ground on this account for esteeming themselves
more rich and more powerful, more free and more happy, than other men who,
whatever be the favors heaped on them by nature and fortune, if destitute of
this philosophy, can never command the realization of all their desires.

In fine, to conclude this code of morals, I thought of reviewing the different
occupations of men in this life, with the view of making choice of the best.
And, without wishing to offer any remarks on the employments of others, I may
state that it was my conviction that I could not do better than continue in
that in which I was engaged, viz., in devoting my whole life to the culture of
my reason, and in making the greatest progress I was able in the knowledge of
truth, on the principles of the method which I had prescribed to myself. This
method, from the time I had begun to apply it, had been to me the source of
satisfaction so intense as to lead me to, believe that more perfect or more
innocent could not be enjoyed in this life; and as by its means I daily
discovered truths that appeared to me of some importance, and of which other
men were generally ignorant, the gratification thence arising so occupied my
mind that I was wholly indifferent to every other object. Besides, the three
preceding maxims were founded singly on the design of continuing the work of
self-instruction. For since God has endowed each of us with some light of
reason by which to distinguish truth from error, I could not have believed that
I ought for a single moment to rest satisfied with the opinions of another,
unless I had resolved to exercise my own judgment in examining these whenever I
should be duly qualified for the task. Nor could I have proceeded on such
opinions without scruple, had I supposed that I should thereby forfeit any
advantage for attaining still more accurate, should such exist. And, in fine, I
could not have restrained my desires, nor remained satisfied had I not followed
a path in which I thought myself certain of attaining all the knowledge to the
acquisition of which I was competent, as well as the largest amount of what is
truly good which I could ever hope to secure Inasmuch as we neither seek nor
shun any object except in so far as our understanding represents it as good or
bad, all that is necessary to right action is right judgment, and to the best
action the most correct judgment, that is, to the acquisition of all the
virtues with all else that is truly valuable and within our reach; and the
assurance of such an acquisition cannot fail to render us contented.

Having thus provided myself with these maxims, and having placed them in
reserve along with the truths of faith, which have ever occupied the first
place in my belief, I came to the conclusion that I might with freedom set
about ridding myself of what remained of my opinions. And, inasmuch as I hoped
to be better able successfully to accomplish this work by holding intercourse
with mankind, than by remaining longer shut up in the retirement where these
thoughts had occurred to me, I betook me again to traveling before the winter
was well ended. And, during the nine subsequent years, I did nothing but roam
from one place to another, desirous of being a spectator rather than an actor
in the plays exhibited on the theater of the world; and, as I made it my
business in each matter to reflect particularly upon what might fairly be
doubted and prove a source of error, I gradually rooted out from my mind all
the errors which had hitherto crept into it. Not that in this I imitated the
sceptics who doubt only that they may doubt, and seek nothing beyond
uncertainty itself; for, on the contrary, my design was singly to find ground
of assurance, and cast aside the loose earth and sand, that I might reach the
rock or the clay. In this, as appears to me, I was successful enough; for,
since I endeavored to discover the falsehood or incertitude of the propositions
I examined, not by feeble conjectures, but by clear and certain reasonings, I
met with nothing so doubtful as not to yield some conclusion of adequate
certainty, although this were merely the inference, that the matter in question
contained nothing certain. And, just as in pulling down an old house, we
usually reserve the ruins to contribute towards the erection, so, in destroying
such of my opinions as I judged to be Ill-founded, I made a variety of
observations and acquired an amount of experience of which I availed myself in
the establishment of more certain. And further, I continued to exercise myself
in the method I had prescribed; for, besides taking care in general to conduct
all my thoughts according to its rules, I reserved some hours from time to time
which I expressly devoted to the employment of the method in the solution of
mathematical difficulties, or even in the solution likewise of some questions
belonging to other sciences, but which, by my having detached them from such
principles of these sciences as were of inadequate certainty, were rendered
almost mathematical: the truth of this will be manifest from the numerous
examples contained in this volume. And thus, without in appearance living
otherwise than those who, with no other occupation than that of spending their
lives agreeably and innocently, study to sever pleasure from vice, and who,
that they may enjoy their leisure without ennui, have recourse to such pursuits
as are honorable, I was nevertheless prosecuting my design, and making greater
progress in the knowledge of truth, than I might, perhaps, have made had I been
engaged in the perusal of books merely, or in holding converse with men of
letters.

These nine years passed away, however, before I had come to any determinate
judgment respecting the difficulties which form matter of dispute among the
learned, or had commenced to seek the principles of any philosophy more certain
than the vulgar. And the examples of many men of the highest genius, who had,
in former times, engaged in this inquiry, but, as appeared to me, without
success, led me to imagine it to be a work of so much difficulty, that I would
not perhaps have ventured on it so soon had I not heard it currently rumored
that I had already completed the inquiry. I know not what were the grounds of
this opinion; and, if my conversation contributed in any measure to its rise,
this must have happened rather from my having confessed my Ignorance with
greater freedom than those are accustomed to do who have studied a little, and
expounded perhaps, the reasons that led me to doubt of many of those things
that by others are esteemed certain, than from my having boasted of any system
of philosophy. But, as I am of a disposition that makes me unwilling to be
esteemed different from what I really am, I thought it necessary to endeavor by
all means to render myself worthy of the reputation accorded to me; and it is
now exactly eight years since this desire constrained me to remove from all
those places where interruption from any of my acquaintances was possible, and
betake myself to this country, in which the long duration of the war has led to
the establishment of such discipline, that the armies maintained seem to be of
use only in enabling the inhabitants to enjoy more securely the blessings of
peace and where, in the midst of a great crowd actively engaged in business,
and more careful of their own affairs than curious about those of others, I
have been enabled to live without being deprived of any of the conveniences to
be had in the most populous cities, and yet as solitary and as retired as in
the midst of the most remote deserts.

PART IV

I am in doubt as to the propriety of making my first meditations in the place
above mentioned matter of discourse; for these are so metaphysical, and so
uncommon, as not, perhaps, to be acceptable to every one. And yet, that it may
be determined whether the foundations that I have laid are sufficiently secure,
I find myself in a measure constrained to advert to them. I had long before
remarked that, in relation to practice, it is sometimes necessary to adopt, as
if above doubt, opinions which we discern to be highly uncertain, as has been
already said; but as I then desired to give my attention solely to the search
after truth, I thought that a procedure exactly the opposite was called for,
and that I ought to reject as absolutely false all opinions in regard to which
I could suppose the least ground for doubt, in order to ascertain whether after
that there remained aught in my belief that was wholly indubitable.
Accordingly, seeing that our senses sometimes deceive us, I was willing to
suppose that there existed nothing really such as they presented to us; and
because some men err in reasoning, and fall into paralogisms, even on the
simplest matters of geometry, I, convinced that I was as open to error as any
other, rejected as false all the reasonings I had hitherto taken for
demonstrations; and finally, when I considered that the very same thoughts
(presentations) which we experience when awake may also be experienced when we
are asleep, while there is at that time not one of them true, I supposed that
all the objects (presentations) that had ever entered into my mind when awake,
had in them no more truth than the illusions of my dreams. But immediately upon
this I observed that, whilst I thus wished to think that all was false, it was
absolutely necessary that I, who thus thought, should be somewhat; and as I
observed that this truth, I think, therefore I am (COGITO ERGO SUM), was so
certain and of such evidence that no ground of doubt, however extravagant,
could be alleged by the sceptics capable of shaking it, I concluded that I
might, without scruple, accept it as the first principle of the philosophy of
which I was in search.

In the next place, I attentively examined what I was and as I observed that I
could suppose that I had no body, and that there was no world nor any place in
which I might be; but that I could not therefore suppose that I was not; and
that, on the contrary, from the very circumstance that I thought to doubt of
the truth of other things, it most clearly and certainly followed that I was;
while, on the other hand, if I had only ceased to think, although all the other
objects which I had ever imagined had been in reality existent, I would have
had no reason to believe that I existed; I thence concluded that I was a
substance whose whole essence or nature consists only in thinking, and which,
that it may exist, has need of no place, nor is dependent on any material
thing; so that “I,” that is to say, the mind by which I am what I
am, is wholly distinct from the body, and is even more easily known than the
latter, and is such, that although the latter were not, it would still continue
to be all that it is.

After this I inquired in general into what is essential to the truth and
certainty of a proposition; for since I had discovered one which I knew to be
true, I thought that I must likewise be able to discover the ground of this
certitude. And as I observed that in the words I think, therefore I am, there
is nothing at all which gives me assurance of their truth beyond this, that I
see very clearly that in order to think it is necessary to exist, I concluded
that I might take, as a general rule, the principle, that all the things which
we very clearly and distinctly conceive are true, only observing, however, that
there is some difficulty in rightly determining the objects which we distinctly
conceive.

In the next place, from reflecting on the circumstance that I doubted, and that
consequently my being was not wholly perfect (for I clearly saw that it was a
greater perfection to know than to doubt), I was led to inquire whence I had
learned to think of something more perfect than myself; and I clearly
recognized that I must hold this notion from some nature which in reality was
more perfect. As for the thoughts of many other objects external to me, as of
the sky, the earth, light, heat, and a thousand more, I was less at a loss to
know whence these came; for since I remarked in them nothing which seemed to
render them superior to myself, I could believe that, if these were true, they
were dependencies on my own nature, in so far as it possessed a certain
perfection, and, if they were false, that I held them from nothing, that is to
say, that they were in me because of a certain imperfection of my nature. But
this could not be the case with-the idea of a nature more perfect than myself;
for to receive it from nothing was a thing manifestly impossible; and, because
it is not less repugnant that the more perfect should be an effect of, and
dependence on the less perfect, than that something should proceed from
nothing, it was equally impossible that I could hold it from myself:
accordingly, it but remained that it had been placed in me by a nature which
was in reality more perfect than mine, and which even possessed within itself
all the perfections of which I could form any idea; that is to say, in a single
word, which was God. And to this I added that, since I knew some perfections
which I did not possess, I was not the only being in existence (I will here,
with your permission, freely use the terms of the schools); but, on the
contrary, that there was of necessity some other more perfect Being upon whom I
was dependent, and from whom I had received all that I possessed; for if I had
existed alone, and independently of every other being, so as to have had from
myself all the perfection, however little, which I actually possessed, I should
have been able, for the same reason, to have had from myself the whole
remainder of perfection, of the want of which I was conscious, and thus could
of myself have become infinite, eternal, immutable, omniscient, all-powerful,
and, in fine, have possessed all the perfections which I could recognize in
God. For in order to know the nature of God (whose existence has been
established by the preceding reasonings), as far as my own nature permitted, I
had only to consider in reference to all the properties of which I found in my
mind some idea, whether their possession was a mark of perfection; and I was
assured that no one which indicated any imperfection was in him, and that none
of the rest was awanting. Thus I perceived that doubt, inconstancy, sadness,
and such like, could not be found in God, since I myself would have been happy
to be free from them. Besides, I had ideas of many sensible and corporeal
things; for although I might suppose that I was dreaming, and that all which I
saw or imagined was false, I could not, nevertheless, deny that the ideas were
in reality in my thoughts. But, because I had already very clearly recognized
in myself that the intelligent nature is distinct from the corporeal, and as I
observed that all composition is an evidence of dependency, and that a state of
dependency is manifestly a state of imperfection, I therefore determined that
it could not be a perfection in God to be compounded of these two natures and
that consequently he was not so compounded; but that if there were any bodies
in the world, or even any intelligences, or other natures that were not wholly
perfect, their existence depended on his power in such a way that they could
not subsist without him for a single moment.

I was disposed straightway to search for other truths and when I had
represented to myself the object of the geometers, which I conceived to be a
continuous body or a space indefinitely extended in length, breadth, and height
or depth, divisible into divers parts which admit of different figures and
sizes, and of being moved or transposed in all manner of ways (for all this the
geometers suppose to be in the object they contemplate), I went over some of
their simplest demonstrations. And, in the first place, I observed, that the
great certitude which by common consent is accorded to these demonstrations, is
founded solely upon this, that they are clearly conceived in accordance with
the rules I have already laid down In the next place, I perceived that there
was nothing at all in these demonstrations which could assure me of the
existence of their object: thus, for example, supposing a triangle to be given,
I distinctly perceived that its three angles were necessarily equal to two
right angles, but I did not on that account perceive anything which could
assure me that any triangle existed: while, on the contrary, recurring to the
examination of the idea of a Perfect Being, I found that the existence of the
Being was comprised in the idea in the same way that the equality of its three
angles to two right angles is comprised in the idea of a triangle, or as in the
idea of a sphere, the equidistance of all points on its surface from the
center, or even still more clearly; and that consequently it is at least as
certain that God, who is this Perfect Being, is, or exists, as any
demonstration of geometry can be.

But the reason which leads many to persuade them selves that there is a
difficulty in knowing this truth, and even also in knowing what their mind
really is, is that they never raise their thoughts above sensible objects, and
are so accustomed to consider nothing except by way of imagination, which is a
mode of thinking limited to material objects, that all that is not imaginable
seems to them not intelligible. The truth of this is sufficiently manifest from
the single circumstance, that the philosophers of the schools accept as a maxim
that there is nothing in the understanding which was not previously in the
senses, in which however it is certain that the ideas of God and of the soul
have never been; and it appears to me that they who make use of their
imagination to comprehend these ideas do exactly the some thing as if, in order
to hear sounds or smell odors, they strove to avail themselves of their eyes;
unless indeed that there is this difference, that the sense of sight does not
afford us an inferior assurance to those of smell or hearing; in place of
which, neither our imagination nor our senses can give us assurance of anything
unless our understanding intervene.

Finally, if there be still persons who are not sufficiently persuaded of the
existence of God and of the soul, by the reasons I have adduced, I am desirous
that they should know that all the other propositions, of the truth of which
they deem themselves perhaps more assured, as that we have a body, and that
there exist stars and an earth, and such like, are less certain; for, although
we have a moral assurance of these things, which is so strong that there is an
appearance of extravagance in doubting of their existence, yet at the same time
no one, unless his intellect is impaired, can deny, when the question relates
to a metaphysical certitude, that there is sufficient reason to exclude entire
assurance, in the observation that when asleep we can in the same way imagine
ourselves possessed of another body and that we see other stars and another
earth, when there is nothing of the kind. For how do we know that the thoughts
which occur in dreaming are false rather than those other which we experience
when awake, since the former are often not less vivid and distinct than the
latter? And though men of the highest genius study this question as long as
they please, I do not believe that they will be able to give any reason which
can be sufficient to remove this doubt, unless they presuppose the existence of
God. For, in the first place even the principle which I have already taken as a
rule, viz., that all the things which we clearly and distinctly conceive are
true, is certain only because God is or exists and because he is a Perfect
Being, and because all that we possess is derived from him: whence it follows
that our ideas or notions, which to the extent of their clearness and
distinctness are real, and proceed from God, must to that extent be true.
Accordingly, whereas we not infrequently have ideas or notions in which some
falsity is contained, this can only be the case with such as are to some extent
confused and obscure, and in this proceed from nothing (participate of
negation), that is, exist in us thus confused because we are not wholly
perfect. And it is evident that it is not less repugnant that falsity or
imperfection, in so far as it is imperfection, should proceed from God, than
that truth or perfection should proceed from nothing. But if we did not know
that all which we possess of real and true proceeds from a Perfect and Infinite
Being, however clear and distinct our ideas might be, we should have no ground
on that account for the assurance that they possessed the perfection of being
true.

But after the knowledge of God and of the soul has rendered us certain of this
rule, we can easily understand that the truth of the thoughts we experience
when awake, ought not in the slightest degree to be called in question on
account of the illusions of our dreams. For if it happened that an individual,
even when asleep, had some very distinct idea, as, for example, if a geometer
should discover some new demonstration, the circumstance of his being asleep
would not militate against its truth; and as for the most ordinary error of our
dreams, which consists in their representing to us various objects in the same
way as our external senses, this is not prejudicial, since it leads us very
properly to suspect the truth of the ideas of sense; for we are not
infrequently deceived in the same manner when awake; as when persons in the
jaundice see all objects yellow, or when the stars or bodies at a great
distance appear to us much smaller than they are. For, in fine, whether awake
or asleep, we ought never to allow ourselves to be persuaded of the truth of
anything unless on the evidence of our reason. And it must be noted that I say
of our reason, and not of our imagination or of our senses: thus, for example,
although we very clearly see the sun, we ought not therefore to determine that
it is only of the size which our sense of sight presents; and we may very
distinctly imagine the head of a lion joined to the body of a goat, without
being therefore shut up to the conclusion that a chimaera exists; for it is not
a dictate of reason that what we thus see or imagine is in reality existent;
but it plainly tells us that all our ideas or notions contain in them some
truth; for otherwise it could not be that God, who is wholly perfect and
veracious, should have placed them in us. And because our reasonings are never
so clear or so complete during sleep as when we are awake, although sometimes
the acts of our imagination are then as lively and distinct, if not more so
than in our waking moments, reason further dictates that, since all our
thoughts cannot be true because of our partial imperfection, those possessing
truth must infallibly be found in the experience of our waking moments rather
than in that of our dreams.

PART V

I would here willingly have proceeded to exhibit the whole chain of truths
which I deduced from these primary but as with a view to this it would have
been necessary now to treat of many questions in dispute among the earned, with
whom I do not wish to be embroiled, I believe that it will be better for me to
refrain from this exposition, and only mention in general what these truths
are, that the more judicious may be able to determine whether a more special
account of them would conduce to the public advantage. I have ever remained
firm in my original resolution to suppose no other principle than that of which
I have recently availed myself in demonstrating the existence of God and of the
soul, and to accept as true nothing that did not appear to me more clear and
certain than the demonstrations of the geometers had formerly appeared; and yet
I venture to state that not only have I found means to satisfy myself in a
short time on all the principal difficulties which are usually treated of in
philosophy, but I have also observed certain laws established in nature by God
in such a manner, and of which he has impressed on our minds such notions, that
after we have reflected sufficiently upon these, we cannot doubt that they are
accurately observed in all that exists or takes place in the world and farther,
by considering the concatenation of these laws, it appears to me that I have
discovered many truths more useful and more important than all I had before
learned, or even had expected to learn.

But because I have essayed to expound the chief of these discoveries in a
treatise which certain considerations prevent me from publishing, I cannot make
the results known more conveniently than by here giving a summary of the
contents of this treatise. It was my design to comprise in it all that, before
I set myself to write it, I thought I knew of the nature of material objects.
But like the painters who, finding themselves unable to represent equally well
on a plain surface all the different faces of a solid body, select one of the
chief, on which alone they make the light fall, and throwing the rest into the
shade, allow them to appear only in so far as they can be seen while looking at
the principal one; so, fearing lest I should not be able to compense in my
discourse all that was in my mind, I resolved to expound singly, though at
considerable length, my opinions regarding light; then to take the opportunity
of adding something on the sun and the fixed stars, since light almost wholly
proceeds from them; on the heavens since they transmit it; on the planets,
comets, and earth, since they reflect it; and particularly on all the bodies
that are upon the earth, since they are either colored, or transparent, or
luminous; and finally on man, since he is the spectator of these objects.
Further, to enable me to cast this variety of subjects somewhat into the shade,
and to express my judgment regarding them with greater freedom, without being
necessitated to adopt or refute the opinions of the learned, I resolved to
leave all the people here to their disputes, and to speak only of what would
happen in a new world, if God were now to create somewhere in the imaginary
spaces matter sufficient to compose one, and were to agitate variously and
confusedly the different parts of this matter, so that there resulted a chaos
as disordered as the poets ever feigned, and after that did nothing more than
lend his ordinary concurrence to nature, and allow her to act in accordance
with the laws which he had established. On this supposition, I, in the first
place, described this matter, and essayed to represent it in such a manner that
to my mind there can be nothing clearer and more intelligible, except what has
been recently said regarding God and the soul; for I even expressly supposed
that it possessed none of those forms or qualities which are so debated in the
schools, nor in general anything the knowledge of which is not so natural to
our minds that no one can so much as imagine himself ignorant of it. Besides, I
have pointed out what are the laws of nature; and, with no other principle upon
which to found my reasonings except the infinite perfection of God, I
endeavored to demonstrate all those about which there could be any room for
doubt, and to prove that they are such, that even if God had created more
worlds, there could have been none in which these laws were not observed.
Thereafter, I showed how the greatest part of the matter of this chaos must, in
accordance with these laws, dispose and arrange itself in such a way as to
present the appearance of heavens; how in the meantime some of its parts must
compose an earth and some planets and comets, and others a sun and fixed stars.
And, making a digression at this stage on the subject of light, I expounded at
considerable length what the nature of that light must be which is found in the
sun and the stars, and how thence in an instant of time it traverses the
immense spaces of the heavens, and how from the planets and comets it is
reflected towards the earth. To this I likewise added much respecting the
substance, the situation, the motions, and all the different qualities of these
heavens and stars; so that I thought I had said enough respecting them to show
that there is nothing observable in the heavens or stars of our system that
must not, or at least may not appear precisely alike in those of the system
which I described. I came next to speak of the earth in particular, and to show
how, even though I had expressly supposed that God had given no weight to the
matter of which it is composed, this should not prevent all its parts from
tending exactly to its center; how with water and air on its surface, the
disposition of the heavens and heavenly bodies, more especially of the moon,
must cause a flow and ebb, like in all its circumstances to that observed in
our seas, as also a certain current both of water and air from east to west,
such as is likewise observed between the tropics; how the mountains, seas,
fountains, and rivers might naturally be formed in it, and the metals produced
in the mines, and the plants grow in the fields and in general, how all the
bodies which are commonly denominated mixed or composite might be generated
and, among other things in the discoveries alluded to inasmuch as besides the
stars, I knew nothing except fire which produces light, I spared no pains to
set forth all that pertains to its nature,–the manner of its production and
support, and to explain how heat is sometimes found without light, and light
without heat; to show how it can induce various colors upon different bodies
and other diverse qualities; how it reduces some to a liquid state and hardens
others; how it can consume almost all bodies, or convert them into ashes and
smoke; and finally, how from these ashes, by the mere intensity of its action,
it forms glass: for as this transmutation of ashes into glass appeared to me as
wonderful as any other in nature, I took a special pleasure in describing it. I
was not, however, disposed, from these circumstances, to conclude that this
world had been created in the manner I described; for it is much more likely
that God made it at the first such as it was to be. But this is certain, and an
opinion commonly received among theologians, that the action by which he now
sustains it is the same with that by which he originally created it; so that
even although he had from the beginning given it no other form than that of
chaos, provided only he had established certain laws of nature, and had lent it
his concurrence to enable it to act as it is wont to do, it may be believed,
without discredit to the miracle of creation, that, in this way alone, things
purely material might, in course of time, have become such as we observe them
at present; and their nature is much more easily conceived when they are beheld
coming in this manner gradually into existence, than when they are only
considered as produced at once in a finished and perfect state.

From the description of inanimate bodies and plants, I passed to animals, and
particularly to man. But since I had not as yet sufficient knowledge to enable
me to treat of these in the same manner as of the rest, that is to say, by
deducing effects from their causes, and by showing from what elements and in
what manner nature must produce them, I remained satisfied with the supposition
that God formed the body of man wholly like to one of ours, as well in the
external shape of the members as in the internal conformation of the organs, of
the same matter with that I had described, and at first placed in it no
rational soul, nor any other principle, in room of the vegetative or sensitive
soul, beyond kindling in the heart one of those fires without light, such as I
had already described, and which I thought was not different from the heat in
hay that has been heaped together before it is dry, or that which causes
fermentation in new wines before they are run clear of the fruit. For, when I
examined the kind of functions which might, as consequences of this
supposition, exist in this body, I found precisely all those which may exist in
us independently of all power of thinking, and consequently without being in
any measure owing to the soul; in other words, to that part of us which is
distinct from the body, and of which it has been said above that the nature
distinctively consists in thinking, functions in which the animals void of
reason may be said wholly to resemble us; but among which I could not discover
any of those that, as dependent on thought alone, belong to us as men, while,
on the other hand, I did afterwards discover these as soon as I supposed God to
have created a rational soul, and to have annexed it to this body in a
particular manner which I described.

But, in order to show how I there handled this matter, I mean here to give the
explication of the motion of the heart and arteries, which, as the first and
most general motion observed in animals, will afford the means of readily
determining what should be thought of all the rest. And that there may be less
difficulty in understanding what I am about to say on this subject, I advise
those who are not versed in anatomy, before they commence the perusal of these
observations, to take the trouble of getting dissected in their presence the
heart of some large animal possessed of lungs (for this is throughout
sufficiently like the human), and to have shown to them its two ventricles or
cavities: in the first place, that in the right side, with which correspond two
very ample tubes, viz., the hollow vein (vena cava), which is the
principal receptacle of the blood, and the trunk of the tree, as it were, of
which all the other veins in the body are branches; and the arterial vein
(vena arteriosa), inappropriately so denominated, since it is in truth
only an artery, which, taking its rise in the heart, is divided, after passing
out from it, into many branches which presently disperse themselves all over
the lungs; in the second place, the cavity in the left side, with which
correspond in the same manner two canals in size equal to or larger than the
preceding, viz., the venous artery (arteria venosa), likewise
inappropriately thus designated, because it is simply a vein which comes from
the lungs, where it is divided into many branches, interlaced with those of the
arterial vein, and those of the tube called the windpipe, through which the air
we breathe enters; and the great artery which, issuing from the heart, sends
its branches all over the body. I should wish also that such persons were
carefully shown the eleven pellicles which, like so many small valves, open and
shut the four orifices that are in these two cavities, viz., three at the
entrance of the hollow veins where they are disposed in such a manner as by no
means to prevent the blood which it contains from flowing into the right
ventricle of the heart, and yet exactly to prevent its flowing out; three at
the entrance to the arterial vein, which, arranged in a manner exactly the
opposite of the former, readily permit the blood contained in this cavity to
pass into the lungs, but hinder that contained in the lungs from returning to
this cavity; and, in like manner, two others at the mouth of the venous artery,
which allow the blood from the lungs to flow into the left cavity of the heart,
but preclude its return; and three at the mouth of the great artery, which
suffer the blood to flow from the heart, but prevent its reflux. Nor do we need
to seek any other reason for the number of these pellicles beyond this that the
orifice of the venous artery being of an oval shape from the nature of its
situation, can be adequately closed with two, whereas the others being round
are more conveniently closed with three. Besides, I wish such persons to
observe that the grand artery and the arterial vein are of much harder and
firmer texture than the venous artery and the hollow vein; and that the two
last expand before entering the heart, and there form, as it were, two pouches
denominated the auricles of the heart, which are composed of a substance
similar to that of the heart itself; and that there is always more warmth in
the heart than in any other part of the body–and finally, that this heat is
capable of causing any drop of blood that passes into the cavities rapidly to
expand and dilate, just as all liquors do when allowed to fall drop by drop
into a highly heated vessel.

For, after these things, it is not necessary for me to say anything more with a
view to explain the motion of the heart, except that when its cavities are not
full of blood, into these the blood of necessity flows,–from the hollow vein
into the right, and from the venous artery into the left; because these two
vessels are always full of blood, and their orifices, which are turned towards
the heart, cannot then be closed. But as soon as two drops of blood have thus
passed, one into each of the cavities, these drops which cannot but be very
large, because the orifices through which they pass are wide, and the vessels
from which they come full of blood, are immediately rarefied, and dilated by
the heat they meet with. In this way they cause the whole heart to expand, and
at the same time press home and shut the five small valves that are at the
entrances of the two vessels from which they flow, and thus prevent any more
blood from coming down into the heart, and becoming more and more rarefied,
they push open the six small valves that are in the orifices of the other two
vessels, through which they pass out, causing in this way all the branches of
the arterial vein and of the grand artery to expand almost simultaneously with
the heart which immediately thereafter begins to contract, as do also the
arteries, because the blood that has entered them has cooled, and the six small
valves close, and the five of the hollow vein and of the venous artery open
anew and allow a passage to other two drops of blood, which cause the heart and
the arteries again to expand as before. And, because the blood which thus
enters into the heart passes through these two pouches called auricles, it
thence happens that their motion is the contrary of that of the heart, and that
when it expands they contract. But lest those who are ignorant of the force of
mathematical demonstrations and who are not accustomed to distinguish true
reasons from mere verisimilitudes, should venture, without examination, to deny
what has been said, I wish it to be considered that the motion which I have now
explained follows as necessarily from the very arrangement of the parts, which
may be observed in the heart by the eye alone, and from the heat which may be
felt with the fingers, and from the nature of the blood as learned from
experience, as does the motion of a clock from the power, the situation, and
shape of its counterweights and wheels.

But if it be asked how it happens that the blood in the veins, flowing in this
way continually into the heart, is not exhausted, and why the arteries do not
become too full, since all the blood which passes through the heart flows into
them, I need only mention in reply what has been written by a physician of
England, who has the honor of having broken the ice on this subject, and of
having been the first to teach that there are many small passages at the
extremities of the arteries, through which the blood received by them from the
heart passes into the small branches of the veins, whence it again returns to
the heart; so that its course amounts precisely to a perpetual circulation. Of
this we have abundant proof in the ordinary experience of surgeons, who, by
binding the arm with a tie of moderate straitness above the part where they
open the vein, cause the blood to flow more copiously than it would have done
without any ligature; whereas quite the contrary would happen were they to bind
it below; that is, between the hand and the opening, or were to make the
ligature above the opening very tight. For it is manifest that the tie,
moderately straightened, while adequate to hinder the blood already in the arm
from returning towards the heart by the veins, cannot on that account prevent
new blood from coming forward through the arteries, because these are situated
below the veins, and their coverings, from their greater consistency, are more
difficult to compress; and also that the blood which comes from the heart tends
to pass through them to the hand with greater force than it does to return from
the hand to the heart through the veins. And since the latter current escapes
from the arm by the opening made in one of the veins, there must of necessity
be certain passages below the ligature, that is, towards the extremities of the
arm through which it can come thither from the arteries. This physician
likewise abundantly establishes what he has advanced respecting the motion of
the blood, from the existence of certain pellicles, so disposed in various
places along the course of the veins, in the manner of small valves, as not to
permit the blood to pass from the middle of the body towards the extremities,
but only to return from the extremities to the heart; and farther, from
experience which shows that all the blood which is in the body may flow out of
it in a very short time through a single artery that has been cut, even
although this had been closely tied in the immediate neighborhood of the heart
and cut between the heart and the ligature, so as to prevent the supposition
that the blood flowing out of it could come from any other quarter than the
heart.

But there are many other circumstances which evince that what I have alleged is
the true cause of the motion of the blood: thus, in the first place, the
difference that is observed between the blood which flows from the veins, and
that from the arteries, can only arise from this, that being rarefied, and, as
it were, distilled by passing through the heart, it is thinner, and more vivid,
and warmer immediately after leaving the heart, in other words, when in the
arteries, than it was a short time before passing into either, in other words,
when it was in the veins; and if attention be given, it will be found that this
difference is very marked only in the neighborhood of the heart; and is not so
evident in parts more remote from it. In the next place, the consistency of the
coats of which the arterial vein and the great artery are composed,
sufficiently shows that the blood is impelled against them with more force than
against the veins. And why should the left cavity of the heart and the great
artery be wider and larger than the right cavity and the arterial vein, were it
not that the blood of the venous artery, having only been in the lungs after it
has passed through the heart, is thinner, and rarefies more readily, and in a
higher degree, than the blood which proceeds immediately from the hollow vein?
And what can physicians conjecture from feeling the pulse unless they know that
according as the blood changes its nature it can be rarefied by the warmth of
the heart, in a higher or lower degree, and more or less quickly than before?
And if it be inquired how this heat is communicated to the other members, must
it not be admitted that this is effected by means of the blood, which, passing
through the heart, is there heated anew, and thence diffused over all the body?
Whence it happens, that if the blood be withdrawn from any part, the heat is
likewise withdrawn by the same means; and although the heart were as-hot as
glowing iron, it would not be capable of warming the feet and hands as at
present, unless it continually sent thither new blood. We likewise perceive
from this, that the true use of respiration is to bring sufficient fresh air
into the lungs, to cause the blood which flows into them from the right
ventricle of the heart, where it has been rarefied and, as it were, changed
into vapors, to become thick, and to convert it anew into blood, before it
flows into the left cavity, without which process it would be unfit for the
nourishment of the fire that is there. This receives confirmation from the
circumstance, that it is observed of animals destitute of lungs that they have
also but one cavity in the heart, and that in children who cannot use them
while in the womb, there is a hole through which the blood flows from the
hollow vein into the left cavity of the heart, and a tube through which it
passes from the arterial vein into the grand artery without passing through the
lung. In the next place, how could digestion be carried on in the stomach
unless the heart communicated heat to it through the arteries, and along with
this certain of the more fluid parts of the blood, which assist in the
dissolution of the food that has been taken in? Is not also the operation which
converts the juice of food into blood easily comprehended, when it is
considered that it is distilled by passing and repassing through the heart
perhaps more than one or two hundred times in a day? And what more need be
adduced to explain nutrition, and the production of the different humors of the
body, beyond saying, that the force with which the blood, in being rarefied,
passes from the heart towards the extremities of the arteries, causes certain
of its parts to remain in the members at which they arrive, and there occupy
the place of some others expelled by them; and that according to the situation,
shape, or smallness of the pores with which they meet, some rather than others
flow into certain parts, in the same way that some sieves are observed to act,
which, by being variously perforated, serve to separate different species of
grain? And, in the last place, what above all is here worthy of observation, is
the generation of the animal spirits, which are like a very subtle wind, or
rather a very pure and vivid flame which, continually ascending in great
abundance from the heart to the brain, thence penetrates through the nerves
into the muscles, and gives motion to all the members; so that to account for
other parts of the blood which, as most agitated and penetrating, are the
fittest to compose these spirits, proceeding towards the brain, it is not
necessary to suppose any other cause, than simply, that the arteries which
carry them thither proceed from the heart in the most direct lines, and that,
according to the rules of mechanics which are the same with those of nature,
when many objects tend at once to the same point where there is not sufficient
room for all (as is the case with the parts of the blood which flow forth from
the left cavity of the heart and tend towards the brain), the weaker and less
agitated parts must necessarily be driven aside from that point by the stronger
which alone in this way reach it I had expounded all these matters with
sufficient minuteness in the treatise which I formerly thought of publishing.
And after these, I had shown what must be the fabric of the nerves and muscles
of the human body to give the animal spirits contained in it the power to move
the members, as when we see heads shortly after they have been struck off still
move and bite the earth, although no longer animated; what changes must take
place in the brain to produce waking, sleep, and dreams; how light, sounds,
odors, tastes, heat, and all the other qualities of external objects impress it
with different ideas by means of the senses; how hunger, thirst, and the other
internal affections can likewise impress upon it divers ideas; what must be
understood by the common sense (sensus communis) in which these ideas
are received, by the memory which retains them, by the fantasy which can change
them in various ways, and out of them compose new ideas, and which, by the same
means, distributing the animal spirits through the muscles, can cause the
members of such a body to move in as many different ways, and in a manner as
suited, whether to the objects that are presented to its senses or to its
internal affections, as can take place in our own case apart from the guidance
of the will. Nor will this appear at all strange to those who are acquainted
with the variety of movements performed by the different automata, or moving
machines fabricated by human industry, and that with help of but few pieces
compared with the great multitude of bones, muscles, nerves, arteries, veins,
and other parts that are found in the body of each animal. Such persons will
look upon this body as a machine made by the hands of God, which is
incomparably better arranged, and adequate to movements more admirable than is
any machine of human invention. And here I specially stayed to show that, were
there such machines exactly resembling organs and outward form an ape or any
other irrational animal, we could have no means of knowing that they were in
any respect of a different nature from these animals; but if there were
machines bearing the image of our bodies, and capable of imitating our actions
as far as it is morally possible, there would still remain two most certain
tests whereby to know that they were not therefore really men. Of these the
first is that they could never use words or other signs arranged in such a
manner as is competent to us in order to declare our thoughts to others: for we
may easily conceive a machine to be so constructed that it emits vocables, and
even that it emits some correspondent to the action upon it of external objects
which cause a change in its organs; for example, if touched in a particular
place it may demand what we wish to say to it; if in another it may cry out
that it is hurt, and such like; but not that it should arrange them variously
so as appositely to reply to what is said in its presence, as men of the lowest
grade of intellect can do. The second test is, that although such machines
might execute many things with equal or perhaps greater perfection than any of
us, they would, without doubt, fail in certain others from which it could be
discovered that they did not act from knowledge, but solely from the
disposition of their organs: for while reason is an universal instrument that
is alike available on every occasion, these organs, on the contrary, need a
particular arrangement for each particular action; whence it must be morally
impossible that there should exist in any machine a diversity of organs
sufficient to enable it to act in all the occurrences of life, in the way in
which our reason enables us to act. Again, by means of these two tests we may
likewise know the difference between men and brutes. For it is highly deserving
of remark, that there are no men so dull and stupid, not even idiots, as to be
incapable of joining together different words, and thereby constructing a
declaration by which to make their thoughts understood; and that on the other
hand, there is no other animal, however perfect or happily circumstanced, which
can do the like. Nor does this inability arise from want of organs: for we
observe that magpies and parrots can utter words like ourselves, and are yet
unable to speak as we do, that is, so as to show that they understand what they
say; in place of which men born deaf and dumb, and thus not less, but rather
more than the brutes, destitute of the organs which others use in speaking, are
in the habit of spontaneously inventing certain signs by which they discover
their thoughts to those who, being usually in their company, have leisure to
learn their language. And this proves not only that the brutes have less reason
than man, but that they have none at all: for we see that very little is
required to enable a person to speak; and since a certain inequality of
capacity is observable among animals of the same species, as well as among men,
and since some are more capable of being instructed than others, it is
incredible that the most perfect ape or parrot of its species, should not in
this be equal to the most stupid infant of its kind or at least to one that was
crack-brained, unless the soul of brutes were of a nature wholly different from
ours. And we ought not to confound speech with the natural movements which
indicate the passions, and can be imitated by machines as well as manifested by
animals; nor must it be thought with certain of the ancients, that the brutes
speak, although we do not understand their language. For if such were the case,
since they are endowed with many organs analogous to ours, they could as easily
communicate their thoughts to us as to their fellows. It is also very worthy of
remark, that, though there are many animals which manifest more industry than
we in certain of their actions, the same animals are yet observed to show none
at all in many others: so that the circumstance that they do better than we
does not prove that they are endowed with mind, for it would thence follow that
they possessed greater reason than any of us, and could surpass us in all
things; on the contrary, it rather proves that they are destitute of reason,
and that it is nature which acts in them according to the disposition of their
organs: thus it is seen, that a clock composed only of wheels and weights can
number the hours and measure time more exactly than we with all our skin.

I had after this described the reasonable soul, and shown that it could by no
means be educed from the power of matter, as the other things of which I had
spoken, but that it must be expressly created; and that it is not sufficient
that it be lodged in the human body exactly like a pilot in a ship, unless
perhaps to move its members, but that it is necessary for it to be joined and
united more closely to the body, in order to have sensations and appetites
similar to ours, and thus constitute a real man. I here entered, in conclusion,
upon the subject of the soul at considerable length, because it is of the
greatest moment: for after the error of those who deny the existence of God, an
error which I think I have already sufficiently refuted, there is none that is
more powerful in leading feeble minds astray from the straight path of virtue
than the supposition that the soul of the brutes is of the same nature with our
own; and consequently that after this life we have nothing to hope for or fear,
more than flies and ants; in place of which, when we know how far they differ
we much better comprehend the reasons which establish that the soul is of a
nature wholly independent of the body, and that consequently it is not liable
to die with the latter and, finally, because no other causes are observed
capable of destroying it, we are naturally led thence to judge that it is
immortal.

PART VI

Three years have now elapsed since I finished the treatise containing all these
matters; and I was beginning to revise it, with the view to put it into the
hands of a printer, when I learned that persons to whom I greatly defer, and
whose authority over my actions is hardly less influential than is my own
reason over my thoughts, had condemned a certain doctrine in physics, published
a short time previously by another individual to which I will not say that I
adhered, but only that, previously to their censure I had observed in it
nothing which I could imagine to be prejudicial either to religion or to the
state, and nothing therefore which would have prevented me from giving
expression to it in writing, if reason had persuaded me of its truth; and this
led me to fear lest among my own doctrines likewise some one might be found in
which I had departed from the truth, notwithstanding the great care I have
always taken not to accord belief to new opinions of which I had not the most
certain demonstrations, and not to give expression to aught that might tend to
the hurt of any one. This has been sufficient to make me alter my purpose of
publishing them; for although the reasons by which I had been induced to take
this resolution were very strong, yet my inclination, which has always been
hostile to writing books, enabled me immediately to discover other
considerations sufficient to excuse me for not undertaking the task. And these
reasons, on one side and the other, are such, that not only is it in some
measure my interest here to state them, but that of the public, perhaps, to
know them.

I have never made much account of what has proceeded from my own mind; and so
long as I gathered no other advantage from the method I employ beyond
satisfying myself on some difficulties belonging to the speculative sciences,
or endeavoring to regulate my actions according to the principles it taught me,
I never thought myself bound to publish anything respecting it. For in what
regards manners, every one is so full of his own wisdom, that there might be
found as many reformers as heads, if any were allowed to take upon themselves
the task of mending them, except those whom God has constituted the supreme
rulers of his people or to whom he has given sufficient grace and zeal to be
prophets; and although my speculations greatly pleased myself, I believed that
others had theirs, which perhaps pleased them still more. But as soon as I had
acquired some general notions respecting physics, and beginning to make trial
of them in various particular difficulties, had observed how far they can carry
us, and how much they differ from the principles that have been employed up to
the present time, I believed that I could not keep them concealed without
sinning grievously against the law by which we are bound to promote, as far as
in us lies, the general good of mankind. For by them I perceived it to be
possible to arrive at knowledge highly useful in life; and in room of the
speculative philosophy usually taught in the schools, to discover a practical,
by means of which, knowing the force and action of fire, water, air the stars,
the heavens, and all the other bodies that surround us, as distinctly as we
know the various crafts of our artisans, we might also apply them in the same
way to all the uses to which they are adapted, and thus render ourselves the
lords and possessors of nature. And this is a result to be desired, not only in
order to the invention of an infinity of arts, by which we might be enabled to
enjoy without any trouble the fruits of the earth, and all its comforts, but
also and especially for the preservation of health, which is without doubt, of
all the blessings of this life, the first and fundamental one; for the mind is
so intimately dependent upon the condition and relation of the organs of the
body, that if any means can ever be found to render men wiser and more
ingenious than hitherto, I believe that it is in medicine they must be sought
for. It is true that the science of medicine, as it now exists, contains few
things whose utility is very remarkable: but without any wish to depreciate it,
I am confident that there is no one, even among those whose profession it is,
who does not admit that all at present known in it is almost nothing in
comparison of what remains to be discovered; and that we could free ourselves
from an infinity of maladies of body as well as of mind, and perhaps also even
from the debility of age, if we had sufficiently ample knowledge of their
causes, and of all the remedies provided for us by nature. But since I designed
to employ my whole life in the search after so necessary a science, and since I
had fallen in with a path which seems to me such, that if any one follow it he
must inevitably reach the end desired, unless he be hindered either by the
shortness of life or the want of experiments, I judged that there could be no
more effectual provision against these two impediments than if I were
faithfully to communicate to the public all the little I might myself have
found, and incite men of superior genius to strive to proceed farther, by
contributing, each according to his inclination and ability, to the experiments
which it would be necessary to make, and also by informing the public of all
they might discover, so that, by the last beginning where those before them had
left off, and thus connecting the lives and labours of many, we might
collectively proceed much farther than each by himself could do.

I remarked, moreover, with respect to experiments, that they become always more
necessary the more one is advanced in knowledge; for, at the commencement, it
is better to make use only of what is spontaneously presented to our senses,
and of which we cannot remain ignorant, provided we bestow on it any
reflection, however slight, than to concern ourselves about more uncommon and
recondite phenomena: the reason of which is, that the more uncommon often only
mislead us so long as the causes of the more ordinary are still unknown; and
the circumstances upon which they depend are almost always so special and
minute as to be highly difficult to detect. But in this I have adopted the
following order: first, I have essayed to find in general the principles, or
first causes of all that is or can be in the world, without taking into
consideration for this end anything but God himself who has created it, and
without educing them from any other source than from certain germs of truths
naturally existing in our minds In the second place, I examined what were the
first and most ordinary effects that could be deduced from these causes; and it
appears to me that, in this way, I have found heavens, stars, an earth, and
even on the earth water, air, fire, minerals, and some other things of this
kind, which of all others are the most common and simple, and hence the easiest
to know. Afterwards when I wished to descend to the more particular, so many
diverse objects presented themselves to me, that I believed it to be impossible
for the human mind to distinguish the forms or species of bodies that are upon
the earth, from an infinity of others which might have been, if it had pleased
God to place them there, or consequently to apply them to our use, unless we
rise to causes through their effects, and avail ourselves of many particular
experiments. Thereupon, turning over in my mind I the objects that had ever
been presented to my senses I freely venture to state that I have never
observed any which I could not satisfactorily explain by the principles had
discovered. But it is necessary also to confess that the power of nature is so
ample and vast, and these principles so simple and general, that I have hardly
observed a single particular effect which I cannot at once recognize as capable
of being deduced in man different modes from the principles, and that my
greatest difficulty usually is to discover in which of these modes the effect
is dependent upon them; for out of this difficulty cannot otherwise extricate
myself than by again seeking certain experiments, which may be such that their
result is not the same, if it is in the one of these modes at we must explain
it, as it would be if it were to be explained in the other. As to what remains,
I am now in a position to discern, as I think, with sufficient clearness what
course must be taken to make the majority those experiments which may conduce
to this end: but I perceive likewise that they are such and so numerous, that
neither my hands nor my income, though it were a thousand times larger than it
is, would be sufficient for them all; so that according as henceforward I shall
have the means of making more or fewer experiments, I shall in the same
proportion make greater or less progress in the knowledge of nature. This was
what I had hoped to make known by the treatise I had written, and so clearly to
exhibit the advantage that would thence accrue to the public, as to induce all
who have the common good of man at heart, that is, all who are virtuous in
truth, and not merely in appearance, or according to opinion, as well to
communicate to me the experiments they had already made, as to assist me in
those that remain to be made.

But since that time other reasons have occurred to me, by which I have been led
to change my opinion, and to think that I ought indeed to go on committing to
writing all the results which I deemed of any moment, as soon as I should have
tested their truth, and to bestow the same care upon them as I would have done
had it been my design to publish them. This course commended itself to me, as
well because I thus afforded myself more ample inducement to examine them
thoroughly, for doubtless that is always more narrowly scrutinized which we
believe will be read by many, than that which is written merely for our private
use (and frequently what has seemed to me true when I first conceived it, has
appeared false when I have set about committing it to writing), as because I
thus lost no opportunity of advancing the interests of the public, as far as in
me lay, and since thus likewise, if my writings possess any value, those into
whose hands they may fall after my death may be able to put them to what use
they deem proper. But I resolved by no means to consent to their publication
during my lifetime, lest either the oppositions or the controversies to which
they might give rise, or even the reputation, such as it might be, which they
would acquire for me, should be any occasion of my losing the time that I had
set apart for my own improvement. For though it be true that every one is bound
to promote to the extent of his ability the good of others, and that to be
useful to no one is really to be worthless, yet it is likewise true that our
cares ought to extend beyond the present, and it is good to omit doing what
might perhaps bring some profit to the living, when we have in view the
accomplishment of other ends that will be of much greater advantage to
posterity. And in truth, I am quite willing it should be known that the little
I have hitherto learned is almost nothing in comparison with that of which I am
ignorant, and to the knowledge of which I do not despair of being able to
attain; for it is much the same with those who gradually discover truth in the
sciences, as with those who when growing rich find less difficulty in making
great acquisitions, than they formerly experienced when poor in making
acquisitions of much smaller amount. Or they may be compared to the commanders
of armies, whose forces usually increase in proportion to their victories, and
who need greater prudence to keep together the residue of their troops after a
defeat than after a victory to take towns and provinces. For he truly engages
in battle who endeavors to surmount all the difficulties and errors which
prevent him from reaching the knowledge of truth, and he is overcome in fight
who admits a false opinion touching a matter of any generality and importance,
and he requires thereafter much more skill to recover his former position than
to make great advances when once in possession of thoroughly ascertained
principles. As for myself, if I have succeeded in discovering any truths in the
sciences (and I trust that what is contained in this volume I will show that I
have found some), I can declare that they are but the consequences and results
of five or six principal difficulties which I have surmounted, and my
encounters with which I reckoned as battles in which victory declared for me. I
will not hesitate even to avow my belief that nothing further is wanting to
enable me fully to realize my designs than to gain two or three similar
victories; and that I am not so far advanced in years but that, according to
the ordinary course of nature, I may still have sufficient leisure for this
end. But I conceive myself the more bound to husband the time that remains the
greater my expectation of being able to employ it aright, and I should
doubtless have much to rob me of it, were I to publish the principles of my
physics: for although they are almost all so evident that to assent to them no
more is needed than simply to understand them, and although there is not one of
them of which I do not expect to be able to give demonstration, yet, as it is
impossible that they can be in accordance with all the diverse opinions of
others, I foresee that I should frequently be turned aside from my grand
design, on occasion of the opposition which they would be sure to awaken.

It may be said, that these oppositions would be useful both in making me aware
of my errors, and, if my speculations contain anything of value, in bringing
others to a fuller understanding of it; and still farther, as many can see
better than one, in leading others who are now beginning to avail themselves of
my principles, to assist me in turn with their discoveries. But though I
recognize my extreme liability to error, and scarce ever trust to the first
thoughts which occur to me, yet-the experience I have had of possible
objections to my views prevents me from anticipating any profit from them. For
I have already had frequent proof of the judgments, as well of those I esteemed
friends, as of some others to whom I thought I was an object of indifference,
and even of some whose malignancy and envy would, I knew, determine them to
endeavor to discover what partiality concealed from the eyes of my friends. But
it has rarely happened that anything has been objected to me which I had myself
altogether overlooked, unless it were something far removed from the subject:
so that I have never met with a single critic of my opinions who did not appear
to me either less rigorous or less equitable than myself. And further, I have
never observed that any truth before unknown has been brought to light by the
disputations that are practised in the schools; for while each strives for the
victory, each is much more occupied in making the best of mere verisimilitude,
than in weighing the reasons on both sides of the question; and those who have
been long good advocates are not afterwards on that account the better judges.

As for the advantage that others would derive from the communication of my
thoughts, it could not be very great; because I have not yet so far prosecuted
them as that much does not remain to be added before they can be applied to
practice. And I think I may say without vanity, that if there is any one who
can carry them out that length, it must be myself rather than another: not that
there may not be in the world many minds incomparably superior to mine, but
because one cannot so well seize a thing and make it one’s own, when it
has been learned from another, as when one has himself discovered it. And so
true is this of the present subject that, though I have often explained some of
my opinions to persons of much acuteness, who, whilst I was speaking, appeared
to understand them very distinctly, yet, when they repeated them, I have
observed that they almost always changed them to such an extent that I could no
longer acknowledge them as mine. I am glad, by the way, to take this
opportunity of requesting posterity never to believe on hearsay that anything
has proceeded from me which has not been published by myself; and I am not at
all astonished at the extravagances attributed to those ancient philosophers
whose own writings we do not possess; whose thoughts, however, I do not on that
account suppose to have been really absurd, seeing they were among the ablest
men of their times, but only that these have been falsely represented to us. It
is observable, accordingly, that scarcely in a single instance has any one of
their disciples surpassed them; and I am quite sure that the most devoted of
the present followers of Aristotle would think themselves happy if they had as
much knowledge of nature as he possessed, were it even under the condition that
they should never afterwards attain to higher. In this respect they are like
the ivy which never strives to rise above the tree that sustains it, and which
frequently even returns downwards when it has reached the top; for it seems to
me that they also sink, in other words, render themselves less wise than they
would be if they gave up study, who, not contented with knowing all that is
intelligibly explained in their author, desire in addition to find in him the
solution of many difficulties of which he says not a word, and never perhaps so
much as thought. Their fashion of philosophizing, however, is well suited to
persons whose abilities fall below mediocrity; for the obscurity of the
distinctions and principles of which they make use enables them to speak of all
things with as much confidence as if they really knew them, and to defend all
that they say on any subject against the most subtle and skillful, without its
being possible for any one to convict them of error. In this they seem to me to
be like a blind man, who, in order to fight on equal terms with a person that
sees, should have made him descend to the bottom of an intensely dark cave: and
I may say that such persons have an interest in my refraining from publishing
the principles of the philosophy of which I make use; for, since these are of a
kind the simplest and most evident, I should, by publishing them, do much the
same as if I were to throw open the windows, and allow the light of day to
enter the cave into which the combatants had descended. But even superior men
have no reason for any great anxiety to know these principles, for if what they
desire is to be able to speak of all things, and to acquire a reputation for
learning, they will gain their end more easily by remaining satisfied with the
appearance of truth, which can be found without much difficulty in all sorts of
matters, than by seeking the truth itself which unfolds itself but slowly and
that only in some departments, while it obliges us, when we have to speak of
others, freely to confess our ignorance. If, however, they prefer the knowledge
of some few truths to the vanity of appearing ignorant of none, as such
knowledge is undoubtedly much to be preferred, and, if they choose to follow a
course similar to mine, they do not require for this that I should say anything
more than I have already said in this discourse. For if they are capable of
making greater advancement than I have made, they will much more be able of
themselves to discover all that I believe myself to have found; since as I have
never examined aught except in order, it is certain that what yet remains to be
discovered is in itself more difficult and recondite, than that which I have
already been enabled to find, and the gratification would be much less in
learning it from me than in discovering it for themselves. Besides this, the
habit which they will acquire, by seeking first what is easy, and then passing
onward slowly and step by step to the more difficult, will benefit them more
than all my instructions. Thus, in my own case, I am persuaded that if I had
been taught from my youth all the truths of which I have since sought out
demonstrations, and had thus learned them without labour, I should never,
perhaps, have known any beyond these; at least, I should never have acquired
the habit and the facility which I think I possess in always discovering new
truths in proportion as I give myself to the search. And, in a single word, if
there is any work in the world which cannot be so well finished by another as
by him who has commenced it, it is that at which I labour.

It is true, indeed, as regards the experiments which may conduce to this end,
that one man is not equal to the task of making them all; but yet he can
advantageously avail himself, in this work, of no hands besides his own, unless
those of artisans, or parties of the same kind, whom he could pay, and whom the
hope of gain (a means of great efficacy) might stimulate to accuracy in the
performance of what was prescribed to them. For as to those who, through
curiosity or a desire of learning, of their own accord, perhaps, offer him
their services, besides that in general their promises exceed their
performance, and that they sketch out fine designs of which not one is ever
realized, they will, without doubt, expect to be compensated for their trouble
by the explication of some difficulties, or, at least, by compliments and
useless speeches, in which he cannot spend any portion of his time without loss
to himself. And as for the experiments that others have already made, even
although these parties should be willing of themselves to communicate them to
him (which is what those who esteem them secrets will never do), the
experiments are, for the most part, accompanied with so many circumstances and
superfluous elements, as to make it exceedingly difficult to disentangle the
truth from its adjuncts–besides, he will find almost all of them so ill
described, or even so false (because those who made them have wished to see in
them only such facts as they deemed conformable to their principles), that, if
in the entire number there should be some of a nature suited to his purpose,
still their value could not compensate for the time what would be necessary to
make the selection. So that if there existed any one whom we assuredly knew to
be capable of making discoveries of the highest kind, and of the greatest
possible utility to the public; and if all other men were therefore eager by
all means to assist him in successfully prosecuting his designs, I do not see
that they could do aught else for him beyond contributing to defray the
expenses of the experiments that might be necessary; and for the rest, prevent
his being deprived of his leisure by the unseasonable interruptions of any one.
But besides that I neither have so high an opinion of myself as to be willing
to make promise of anything extraordinary, nor feed on imaginations so vain as
to fancy that the public must be much interested in my designs; I do not, on
the other hand, own a soul so mean as to be capable of accepting from any one a
favor of which it could be supposed that I was unworthy.

These considerations taken together were the reason why, for the last three
years, I have been unwilling to publish the treatise I had on hand, and why I
even resolved to give publicity during my life to no other that was so general,
or by which the principles of my physics might be understood. But since then,
two other reasons have come into operation that have determined me here to
subjoin some particular specimens, and give the public some account of my
doings and designs. Of these considerations, the first is, that if I failed to
do so, many who were cognizant of my previous intention to publish some
writings, might have imagined that the reasons which induced me to refrain from
so doing, were less to my credit than they really are; for although I am not
immoderately desirous of glory, or even, if I may venture so to say, although I
am averse from it in so far as I deem it hostile to repose which I hold in
greater account than aught else, yet, at the same time, I have never sought to
conceal my actions as if they were crimes, nor made use of many precautions
that I might remain unknown; and this partly because I should have thought such
a course of conduct a wrong against myself, and partly because it would have
occasioned me some sort of uneasiness which would again have been contrary to
the perfect mental tranquillity which I court. And forasmuch as, while thus
indifferent to the thought alike of fame or of forgetfulness, I have yet been
unable to prevent myself from acquiring some sort of reputation, I have thought
it incumbent on me to do my best to save myself at least from being ill-spoken
of. The other reason that has determined me to commit to writing these
specimens of philosophy is, that I am becoming daily more and more alive to the
delay which my design of self-instruction suffers, for want of the infinity of
experiments I require, and which it is impossible for me to make without the
assistance of others: and, without flattering myself so much as to expect the
public to take a large share in my interests, I am yet unwilling to be found so
far wanting in the duty I owe to myself, as to give occasion to those who shall
survive me to make it matter of reproach against me some day, that I might have
left them many things in a much more perfect state than I have done, had I not
too much neglected to make them aware of the ways in which they could have
promoted the accomplishment of my designs.

And I thought that it was easy for me to select some matters which should
neither be obnoxious to much controversy, nor should compel me to expound more
of my principles than I desired, and which should yet be sufficient clearly to
exhibit what I can or cannot accomplish in the sciences. Whether or not I have
succeeded in this it is not for me to say; and I do not wish to forestall the
judgments of others by speaking myself of my writings; but it will gratify me
if they be examined, and, to afford the greater inducement to this I request
all who may have any objections to make to them, to take the trouble of
forwarding these to my publisher, who will give me notice of them, that I may
endeavor to subjoin at the same time my reply; and in this way readers seeing
both at once will more easily determine where the truth lies; for I do not
engage in any case to make prolix replies, but only with perfect frankness to
avow my errors if I am convinced of them, or if I cannot perceive them, simply
to state what I think is required for defense of the matters I have written,
adding thereto no explication of any new matte that it may not be necessary to
pass without end from one thing to another.

If some of the matters of which I have spoken in the beginning of the
“Dioptrics” and “Meteorics” should offend at first
sight, because I call them hypotheses and seem indifferent about giving proof
of them, I request a patient and attentive reading of the whole, from which I
hope those hesitating will derive satisfaction; for it appears to me that the
reasonings are so mutually connected in these treatises, that, as the last are
demonstrated by the first which are their causes, the first are in their turn
demonstrated by the last which are their effects. Nor must it be imagined that
I here commit the fallacy which the logicians call a circle; for since
experience renders the majority of these effects most certain, the causes from
which I deduce them do not serve so much to establish their reality as to
explain their existence; but on the contrary, the reality of the causes is
established by the reality of the effects. Nor have I called them hypotheses
with any other end in view except that it may be known that I think I am able
to deduce them from those first truths which I have already expounded; and yet
that I have expressly determined not to do so, to prevent a certain class of
minds from thence taking occasion to build some extravagant philosophy upon
what they may take to be my principles, and my being blamed for it. I refer to
those who imagine that they can master in a day all that another has taken
twenty years to think out, as soon as he has spoken two or three words to them
on the subject; or who are the more liable to error and the less capable of
perceiving truth in very proportion as they are more subtle and lively. As to
the opinions which are truly and wholly mine, I offer no apology for them as
new,–persuaded as I am that if their reasons be well considered they will be
found to be so simple and so conformed, to common sense as to appear less
extraordinary and less paradoxical than any others which can be held on the
same subjects; nor do I even boast of being the earliest discoverer of any of
them, but only of having adopted them, neither because they had nor because
they had not been held by others, but solely because reason has convinced me of
their truth.

Though artisans may not be able at once to execute the invention which is
explained in the “Dioptrics,” I do not think that any one on that
account is entitled to condemn it; for since address and practice are required
in order so to make and adjust the machines described by me as not to overlook
the smallest particular, I should not be less astonished if they succeeded on
the first attempt than if a person were in one day to become an accomplished
performer on the guitar, by merely having excellent sheets of music set up
before him. And if I write in French, which is the language of my country, in
preference to Latin, which is that of my preceptors, it is because I expect
that those who make use of their unprejudiced natural reason will be better
judges of my opinions than those who give heed to the writings of the ancients
only; and as for those who unite good sense with habits of study, whom alone I
desire for judges, they will not, I feel assured, be so partial to Latin as to
refuse to listen to my reasonings merely because I expound them in the vulgar
tongue.

In conclusion, I am unwilling here to say anything very specific of the
progress which I expect to make for the future in the sciences, or to bind
myself to the public by any promise which I am not certain of being able to
fulfill; but this only will I say, that I have resolved to devote what time I
may still have to live to no other occupation than that of endeavoring to
acquire some knowledge of Nature, which shall be of such a kind as to enable us
therefrom to deduce rules in medicine of greater certainty than those at
present in use; and that my inclination is so much opposed to all other
pursuits, especially to such as cannot be useful to some without being hurtful
to others, that if, by any circumstances, I had been constrained to engage in
such, I do not believe that I should have been able to succeed. Of this I here
make a public declaration, though well aware that it cannot serve to procure
for me any consideration in the world, which, however, I do not in the least
affect; and I shall always hold myself more obliged to those through whose
favor I am permitted to enjoy my retirement without interruption than to any
who might offer me the highest earthly preferments.