Then Again




Rene Descartes

Discourse on Method



Rene Descartes (1596-1650) is generally regarded as the founder of modern philosophy. He was schooled in the scholastic philosophy which had its roots in the philosophy of Ancient Greece. The work which is excerpted here is an attempt to uncover a new foundation for rational knowledge. The selection begins with an autobiographical introduction and concludes with a "thought experiment." 

Part One

From my childhood I lived in a world of books, and since I was taught that by their help I could gain a clear and assured knowledge of everything useful in life, I was eager to learn from them. But as soon as I had finished the course of studies which usually admits one to the ranks of the learned, I changed my opinion completely. For I found myself saddled with so many doubts and errors that I seemed to have gained nothing in trying to educate myself unless it was to discover more and more fully how ignorant I was.

Nevertheless I had been in one of the most celebrated schools in Europe, where I thought there should be wise men if wise men existed anywhere on earth. I had learned there everything that others learned, and, not satisfied with merely the knowledge that was taught, I had perused as many books as I could find which contained more unusual and recondite knowledge . . . And finally, it did not seem to me that our times were less flourishing and fertile than were any of the earlier periods. All this led me to conclude that I could judge others by myself, and to decide that there was no such wisdom in the world as I had previously hoped to find . . .

I revered our theology, and hoped as much as anyone else to get to heaven, but having learned on great authority that the road was just as open to the most ignorant as to the most learned, and that the truths of revelation which lead thereto are beyond our understanding, I would not have dared to submit them to the weakness of my reasonings. I thought that to succeed in their examination it would be necessary to have some extraordinary assistance from heaven, and to be more than a man.

I will say nothing of philosophy except that it has been studied for many centuries by the most outstanding minds without having produced anything which is not in dispute and consequently doubtful. I did not have enough presumption to hope to succeed better than the others; and when I noticed how many different opinions learned men may hold on the same subject, despite the fact that no more than one of them can ever be right, I resolved to consider almost as false any opinion which was merely plausible . . .

This is why I gave up my studies entirely as soon as I reached the age when I was no longer under the control of my teachers. I resolved to seek no other knowledge than that which I might find within myself, or perhaps in the great book of nature. I spent a few years of my adolescence traveling, seeing courts and armies, living with people of diverse types and stations of life, acquiring varied experience, testing myself in the episodes which fortune sent me, and, above all, thinking about the things around me so that I could derive some profit from them. For it seemed to me that I might find much more of the truth in the cogitations [reflections] which each man made on things which were important to him, and where he would be the loser if he judged badly, than in the cogitations of a man of letters in his study, concerned with speculations which produce no effect, and which have no consequences to him . . .

After spending several years in thus studying the book of nature and acquiring experience, I eventually reached the decision to study my own self and to employ all my abilities to try to choose the right path. This produced much better results in my case, I think, than would have been produced if I had never left my books and my country . . .

Part Two

. . . As far as the opinions which I had been receiving since my birth were concerned, I could not do better than to reject them completely for once in my lifetime and to resume them afterwards, or perhaps accept better ones in their place, when I had determined how they fitted into a rational scheme. And I firmly believed that by this means I would succeed in conducting my life much better than if I built only upon the old foundations and gave credence to the principles which I had acquired in my childhood without ever having examined them to see whether they were true or not . . .

. . . Never has my intention been more than to try to reform my own ideas, and rebuild them on foundations that would be wholly mine . . . The decision to abandon all one's preconceived notions is not an example for all to follow . . .

As for myself, I should no doubt have . . . [never attempted it] if I had had but a single teacher or if I had not known the differences which have always existed among the most learned. I had discovered in college that one cannot imagine anything so strange and unbelievable but that it has been upheld by some philosopher; and in my travels I had found that those who held opinions contrary to ours were neither barbarians nor savages, but that many of them were at least as reasonable as ourselves. I had considered how the same man, with the same capacity for reason, becomes different as a result of being brought up among Frenchmen or Germans than he would be if he had been brought up among Chinese or cannibals; and how, in our fashions, the thing which pleased us ten years ago and perhaps will please us again ten years in the future, now seems extravagant and ridiculous; and I felt that in all these ways we are much more greatly influenced by custom and example than by any certain knowledge. Faced with this divergence of opinion, I could not accept the testimony of the majority, for I thought it worthless as a proof of anything somewhat difficult to discover, since it is much more likely that a single man will have discovered it than a whole people. Nor, on the other hand, could I select anyone whose opinions seemed to me to be preferable to those of others, and I was thus constrained to embark on the investigation for myself.

Nevertheless, like a man who walks alone in the darkness, I resolved to go so slowly and circumspectly that if I did not get ahead very rapidly I was at least safe from falling. Also, I did not want to reject all the opinions which had slipped irrationally into my consciousness since birth until I had first spent enough time planning how to accomplish the task which I was then undertaking, and seeking the true method of obtaining knowledge of everything which my mind was capable of understanding . . .

* * *

The method which Descartes develops is based on the model of geometry. Beginning with a set of axioms, one then uses reason and logic to disclose truth.

. . . I thought that some other method [beside that of logic, algebra, and geometry] must be found to combine the advantages of these three and to escape their faults. Finally, just as the multitude of laws frequently furnishes an excuse for vice, and a state is much better governed with a few laws which are strictly adhered to, so I thought that instead of the great number of precepts of which logic is composed, I would have enough with the four following ones, provided that I made a firm and unalterable resolution not to violate them even in a single instance.

The first rule was never to accept anything as true unless I recognized it to be evidently such: that is, carefully to avoid precipitation and prejudgment, and to include nothing in my conclusions unless it presented itself so clearly and distinctly to my mind that there was no occasion to doubt it.

The second was to divide each of the difficulties which I encountered into as many parts as possible, and as might be required for an easier solution.

The third was to think in an orderly fashion, beginning with the things which were simplest and easiest to understand, and gradually and by degrees reaching toward more complex knowledge, even treating as though ordered materials which were not necessarily so.

The last was always to make enumerations so complete, and reviews so general, that I would be certain that nothing was omitted . . .

What pleased me most about this method was that it enabled me to reason in all things, if not perfectly, at least as well as was in my power. In addition, I felt that in practicing it my mind, I was gradually becoming accustomed to conceive its objects more clearly and distinctly . . .

* * *

The key to his method was finding an incontrovertible truth which could serve as an axiom for his system. To find this axiom, he presents a thought experiment. He examines all of the things he thinks he knows to find any which cannot be doubted. This procedure becomes known as "radical doubt."

Part Four

As I desired to devote myself wholly to the . . . search for truth, I thought that I should . . . reject as absolutely false anything of which I could have the least doubt, in order to see whether anything would be left after this procedure which could be called wholly certain. Thus, as our senses deceive us at times, I was ready to suppose that nothing was at all the way our senses represented them to be. As there are men who make mistakes in reasoning even on the simplest topics in geometry, I judged that I was as liable to error as any other, and rejected as false all the reasoning which I had previously accepted as valid demonstration. Finally, as the same precepts which we have when awake may come to us when asleep without their being true, I decided to suppose that nothing that had ever entered my mind was more real than the illusions of my dreams. But I soon noticed that while I thus wished to think everything false, it was necessarily true that I who thought so was something. Since this truth, I think, therefore I am, was so firm and assured that all the most extravagant suppositions of the skeptics' were unable to shake it, I judged that I could safely accept it as the first principle of the philosophy I was seeking.

From: Rene Descartes, Discourse on Method, Laurence Lafleur, trans., (New York; Macmillan, 1960). Reprinted in Marvin Perry, et. al. eds., Sources of the Western Tradition, Vol. II, 3rd ed., (Boston; Houghton Mifflin, 1995) pp. 46-49.

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