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Discourse on Method

(Discours de la méthode)

René Descartes


(A scientist-philosopher wishes that all the deep questions of life could be as certain as his mathematical results—so he decides to start from scratch and make them that way.)

Figures 32 and 33 in L’Homme (Man), Descartes’ 1633 work, illustrating the accordance of the operation of the human body with mathematical principles.

The influence this little book has had over the past few centuries is (to make a ridiculous understatement) vastly out of proportion to its size.  It is manageable in a single evening sitting, or (as Descartes is kind enough to inform us) in six roughly equal short sittings.  My recent reading of it was over breakfast.  It is strange to think that one can read a book so illustrious and philosophical over breakfast, but such is Descartes’ charm.  He is of course a philosopher of the highest rank: the cogiter of that most famous phrase in the history of thought, cogito ergo sum.  He is one of the chief inspirations for the modern movement in philosophy in which we still are steeped today, which emphasizes, among other things, a systematic and reasoned approach to all matters of inquiry in an effort to gain a scientific understanding of everything there is to know.  Yet, again, the charm of Descartes is that he gives us this little journal, this series of ideas, as if he were chatting to us in front of a fire.  He tells us how he came to think the way he does about things, rather than giving us “the way things are” in an authoritative or textbook manner.  By this strategy he draws us in, perhaps unawares.  This is an important quality to recognize in Descartes today, or at least it was for me.  For I, like most students over the last fifty years or so, was warned about Descartes in college, as a naughty modernist, a reductionist, a disenchanter, a rationalist.  What dry and impersonal words these are, and yet how personal is the Discourse compared with most philosophical writings!  The criticisms may very well be true of his system, but there is more to this book than just a set of statements—we get to meet an author, a person.  We should meet someone before we criticize him too harshly; often knowing the person tempers our antagonism.

But we cannot let Descartes off the hook, all the same.  His championship of the then newborn scientific enterprise has obviously been rewarded, as science since his time has made such amazing and useful discoveries (useful both in a philosophical, world-view-molding sense, and also in a utilitarian or practical sense) that Descartes himself would undoubtedly be astounded. However, as far as I can see, his major fault is that he didn’t follow his own first rule!  This rule was that he would refuse to accept anything unless it is beyond doubt.  His conclusions, if they were beyond all doubt for him, surely are not beyond all doubt for all readers.  For example, in fact the prime example, no support is offered for the stupendous assumption that the geometer’s or mathematician’s method is the only way to acquire knowledge, nor do we have any reason to believe that the answers to mankind’s deepest questions can be known through that means.  And, as we might expect, his conclusions regarding the duality of the body and soul, the existence of God, the metaphysical facts that supposedly follow from the circulation of the blood, the nature of human reason, the uniqueness of humans, and the creation of the world, are none of them demonstrated in the same way as a geometric proof is.  By this I do not mean that they are not analytically demonstrated (shown to be true regardless of empirical evidence).  Although that is true, my point is that he has not given us conclusions that are as certain as those mathematical sciences produce.  Yet this was his major project, to build a worldview with such certainty.  This criticism may seem harsh and sweeping, but I cannot help thinking that Descartes failed his own rigorous tests.  For instance, is it really a logical progression that admits of no doubt to proceed as follows?:

Premise 1.  The existence of my mind is not open to doubt.
Premise 2.  The existence of my body is open to doubt. Therefore,
Conclusion:  I am a mind that is not dependent on a body for its existence.

This is of course fallacious.  Just because two entities do not share the same status as far as our certainty of their existence is concerned, does not license any conclusion regarding their existence, or their dependence of the two entities on each other—namely, their ontological status.  To make such a claim is to confuse knowledge about existence with existence itself.  I am not trying to say that all of Descartes’s conclusions are unwarranted or that he was a sloppy thinker; rather, this example just illustrates that he did not stick very rigidly to his own program, often on some pretty heavy subjects.

To be fair, Descartes may not be providing us, in fact he is not providing us, with the particular modes of reasoning, the quasi-mathematical proofs, so to speak, which can be used to produce these conclusions.  He wanted to inspire us to search for them; and I am here analyzing his logic partly because of the effect of his inspiration down through the centuries.  But I don’t think these proofs exist—I think they cannot exist.  The reason why thousands of years of philosophy have passed without agreement on fundamental philosophical questions is, I suspect, because the way we gain knowledge of such things is not by the same method that we gain mathematical or even most scientific knowledge.  Or, to say it another way, what we mean by “knowledge” is very different in the two realms.  Deep philosophical truths are not demonstrable in the same way as the Pythagorean theorem or the circulation of blood.  So, as laudable as Descartes’ quest for mathematically certain knowledge is, if he is really committed to this quest, he might not make it much further than his cogito ergo sum.  He might even have to remain one who believes only in the existence of his own mind.  And that point is certain, if at all, only to the one doing the thinking.  This sad state surely must lead us to suspect that there is something wrong with the project itself, with the limitations Descartes has placed on his search for truth.

Even given these criticisms and others, not even for a second would I wish for the removal of Discourse on Method from the lofty status it has enjoyed in the history of thought.  Besides its importance to philosophy proper, it has had a tremendously powerful and beneficial influence on the growth of rational thought and scientific understanding of the universe.  Descartes has suffered a bad rap for his faults (and those of his followers!), but it is time we get mature and admit that his emphasis on reason and critical thinking has done our civilization a great service.  In fact, even his faults are important as they teach an important lesson to us as humans.  The Discourse portrays an ambitious attempt at omniscience from a capable thinker, a drive towards complete knowledge by means of a single method.  One may look at the results with some misgiving, but in Descartes’s attempt we all can perhaps see ourselves, trying to answer the same questions, and willing to go to extremes also if that will help us get somewhere.  Anything, to get rid of uncertainty!  Searchers for truth hate uncertainty!  What a great worldview we’d have without uncertainty!  But the lesson here is that Descartes, not surprisingly, failed in this superhuman part of his project.  Uncertainty is the nature of the human condition.  He couldn’t get rid of it for us.  The tools that give us impressive results in one area of inquiry will not necessarily be a panacea for all of our ignorance.  Perhaps there is no panacea.  Perhaps we’re not capable of omniscience, or do not have the tools.  Perhaps this should make us humble, yet critical, and ready to catch what knowledge we can, however we can, and to balance our restlessness with caution when dealing with whatever uncertainty we cannot remove.

A note on the famous “cogito”.  I remember how I erroneously interpreted those words “I think, therefore I am” when I first heard them as a kid.  I thought it was a sort of moral lesson: “The reason why I exist, or my best excuse for existing, is that I am thinking,” the unsaid second half of this being something like So you’d better darn well use your brain or you either won’t exist, or at least you won’t deserve it!  Psychoanalyze my young self as you might, this is what I thought it meant.  Anyway, what a monumental phrase, and we have it right here!  Towards the beginning of the fourth section (see below under Tidbits) sits that iconic passage!  Well, not quite.  In the 1637 Discourse he was writing in French, “je pense, donc je suis”.  Not until his Latin work Principia Philosophiae in 1644 does he actually write “ego cogito, ergo sum”.  We shorten this to “cogito ergo sum” with little loss of meaning, as the subject “ego”, “I”, is also indicated by the –o ending of “cogito”.  As in modern Spanish for instance, the first person pronoun in Latin is usually reserved for cases when the speaker seeks to stress it.  This is indeed one of those cases—it is precisely the fact that I am thinking that necessitates that there be some person existing who is doing that thinking.  I suspect more students would understand and recognize the prodigious weight of the cogito (what a stupendous idea it is!) if its perennial form included that first word “Ego”.  Since I am thinking, there must be an I— I cannot doubt my own existence!  I must exist!



The full translated title is Discourse on the Method of Rightly Conducting the Reason, and Seeking Truth in the Sciences (originally printed as an introduction to his scientific works of that year: DioptricMeteors, and Geometry).

Descartes begins by claiming that he wishes to have the healthiest and most reasonable mind—to apply his reason correctly (for reason is given to all, he tells us, and variety of opinion proceeds from an error in the application of it).  He believes that the search for truth is the only worthwhile occupation for man, so he resolves to join it, but to do so with proper humility.

He requires a method for the search for truth. Various disciplines seem to be better or worse, but mathematics seems to be the best in terms of producing very certain demonstrations of its conclusions; math will serve, then, as his model method.  He is skeptical, on the other hand, about traditional speculative means of philosophy, and about taking things on authority.  So he resolves to construct his world-view from the ground up, only on the most secure principles; he recognizes that this dangerous and difficult project is not for many people, and hopes that nobody thinks he is advocating reckless liberalism.  He establishes four rules that he will follow throughout the project: (1) he will refuse to accept anything unless it is beyond doubt; (2) he will divide every issue into as many parts as possible to solve it; (3) he will start with the simplest issues and work up to the more complicated; and (4) he will assure himself that he hasn’t overlooked anything by reviewing all of his subjects completely and generally.  He then moves forward by making an assumption that all the knowledge he may find will be attainable by the use of the same types of reasoning that the mathematicians use.  He adopts a provisional morality to use in the interim, until he can come up with one based on a secure footing.

To begin his exploration, he finds that the only thing about which he is incapable of doubt is his own existence, because his very contemplation of it rules out the possibility of his nonexistence. So he starts here.  The next thing he is forced to realize is his imperfection, which leads him to postulate the existence of a perfect God which makes sense of this realization.  Descartes deduces the nature of God from his own nature, minus any imperfection.  Moreover, one of the attributes of a perfect God is existence, so God must exist.  We also need God for our belief in what we sense, for the senses themselves are untrustworthy.  We have been given Reason to filter our sense experience and draw trustworthy conclusions from it.

With this method Descartes assures us that he has made great headway, and gives us a little taste of what he has concluded.  For instance, the world could have been created gradually, by fixed laws acting on an initial chaos of matter.  But, since there doesn’t seem to be any evidence for such a gradual creation of humanity, he remains satisfied with the traditional instantaneous special creation of man.  Additional insights are gained by his understanding of the circulation of the blood, and the uniqueness of humans (e.g. in their language and reason).  Reason does not seem to be a natural part of man, but must have been added during our history.

Some of his results might hurt people, so he would refrain from publishing those; but some will help, such as the idea of his that medicine could become a science.  What we need in order for science to flourish is a unified peer-group of experimental scientists devoted to answering certain questions.  And science is such that small victories will beget greater victories.  Opposition will certainly arise, but this is all part of the process.  There are also faults with science that need to be remedied: one is inadequate design and controls, and the other is bias.  With all of this in mind, we can look hopefully to the future of the scientific enterprise, and therein the search for truth.

According to Descartes’ Prefatory note, the six sections of the work are as follows:

  1. Various considerations touching the Sciences
  2. The principal rules of the Method which the Author has discovered
  3. Certain of the rules of Morals which he has deduced from this Method
  4. The reasonings by which he establishes the existence of God and of the Human Soul
  5. 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
  6. 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

These are all reasonable descriptions of the sections, except the third.  He assuredly does not do as he had planned (evidently) and deduce from this Method any morals.  Rather, he adopts a provisional morality as an expedient until such time as his Method could be developed and used to its full potential.  Needless to say, the time when he could use a scientific method to deduce morals never arrived for René, nor has it arrived in the next four hundred years since in the hands of his followers in this venture, from the Cartesians to E. O. Wilson.

Tidbits of Significance 

(translated from the French by John Veitch):

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.

-I, initial sentence.


…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.



…reason or sense… is that alone which constitutes us men, and distinguishes us from the brutes.



…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 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.



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.



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 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.



…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 leant upon principles which, in my youth, I had taken upon trust.



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.



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 one of the philosophers.



…the ground of our opinions is far more custom and example than any certain knowledge.



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.



…a multitude of laws often only hampers justice, so that a state is best governed when, with few laws, these are rigidly administered.



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.



…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.



…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.

-III, [very reminiscent of the Stoics].


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.



…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, 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.

-IV, [the Cogito].


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 recognised that I must hold this notion from some nature which in reality was more perfect.



But the reason which leads many to persuade themselves that there is a difficulty in knowing this truth [that God exists], 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.



…it appears to me that they who make use of their imagination to comprehend these ideas do exactly the same thing as if, in order to hear sounds or smell odours, they strove to avail themselves of their eyes.



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.



…I found means to satisfy myself in a short time on all the principal difficulties which are usually treated of in philosophy.



But this is certain, and an opinion commonly received among theologians, that the action by which he [God] now sustains is the same with that by which he originally created it [the world]; 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.

-V, [notice how this presages the concept of evolution, a hitherto undreamt idea].


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.



…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 must 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.



For in what regards manners, every one is so full of his own wisdom, that there might be found as many reformers as heads.



…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.



…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.



…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 use to posterity.



…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 endeavours to surmount all of 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.



…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.



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.

-VI, [How foresightful—beware the Cartesians!]


…the reality of the causes is established by the reality of the effects.



“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 myslf more obliged to those through whose favour I am permitted to enjoy my retirement without interruption than to any who might offer me the highest earthly preferments.”

-VI, (final sentence, after promising that he will spend the rest of his career searching for knowledge of nature, especially for the purpose of placing medicine on a reliable scientific basis).



…you are sick of being uncertain of life’s questions, and are curious to see how someone tried to build a reasonable and solid world-view;


…you would like to see one of the first modern scientists give his plug for the new enterprise.



(for the metaphysical meditator:)

  • Aristotle, Metaphysics  (4th century BC).
  • David Hume, A Treatise of Human Nature  (1737).
  • Immanuel Kant, Critique of Pure Reason  (1781).
  • John Dewey, The Quest for Certainty  (1929).

 (for the early modern philosopher-scientist:)

  • Francis Bacon, Novum Organum  (1620).
  • Galileo Galilei, Dialogue Concerning the Two Chief World Systems  (1632).
  • René Descartes, Meditations on the First Philosophy  (1641).
  • Robert Boyle, The Sceptical Chymist  (1661).

Find It!

Hardcover: Another shocker– no reputable hardcover edition is widely available. Here’s a “Royal Collector’s Edition“; but for more affordability go used (look for the old Everyman for instance). 

Paperback: Plenty of paperback versions exist, as this book is regularly assigned in philosophy and Renaissance/Early Modern courses.  Here is the Oxford World Classics edition, with Renaissance scholar Ian Maclean translating.

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