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René Descartes
Discourse on Method

Squashed down to read in about 25 minutes
"Cogito, ergo sum (I think, therefore I am)"

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INTRODUCTION TO Discourse on Method

Doubt, not scepticism, was Descartes's philosophic starting point. Warned by the fate of Galileo, he withheld from publication during his lifetime his treatise on The World which he had finished in 1633. His search after philosophical certainty is explained in the Discourse on Method published in 1637. In 1641 he published Meditationes and he dealt with morals in Principia Philosophiae, and Traite des Passions de L'Ame. Descartes stands at the head of the school of mathematicians which linked up the mathematics of the Renaissance with modern mathematical writings. The invention of analytical geometry dates from the publication of his Geometry. His Discourse on Method is a landmark in the modern history of philosophic thought.


The is the condensed version first published by Sir John Hammerton in 1919. It misses out some important bits, and I really must get round to improving it.


René Descartes, 1637
Discourse on Method

"Cogito, ergo sum (I think, therefore I am)"

No man ever desires more Good sense than he has, so this shows that reason is by nature equal in all men. If there is diversity of opinion, this arises from the fact that we conduct our thought by different ways and consider different things. In philosophy there is no truth which is not disputed; the other sciences all borrow their principles from philosophy.
I considered that as, during our childhood, we had been governed by our appetites and our tutors, that I might pull down the edifice of old thoughts and establish new. And as a state is better governed which has but few laws, I believed that I should find sufficient these four precepts:
1: Never to accept anything as true when I did not recognize it clearly to be so
2: Divide up the difficulties which I should examine into as many parts as possible, for their better solution.
3: conduct my thoughts in order, by beginning with the simplest objects.
4: Be sure of omitting nothing.
I must have a rule of life as a shelter while my new house was in building, and this consisted of maxims.
1: To conform myself to the laws and customs and religion of my country.
2: To follow resolutely even doubtful opinions when sure opinions were not available
3: Always to conquer myself rather than fortune
4: Persevere in my occupations
But, because our senses sometimes deceive us, I was likely to err. So I tried to reject all which I had formerly accepted as no more truth than the illusion of my dreams. But I observed that the I who thought must of necessity be somewhat; so that - I think, therefore I am - was so entirely firm and assured that I could unhesitatingly accept it as the first principle of the philosophy.
But, reflecting that I could doubt, and so was obviously not perfect, I knew that I had knowledge of something else, namely something perfect, and tried to think what it might be. It is God.

The Squashed Philosophers Edition of...

Discourse on Method
René Descartes
Squashed version edited by Glyn Hughes © 2011

Discourse on Method of Rightly Conducting Reason, and Seeking Truth in the Sciences


GOOD sense must be better distributed than anything else in the world, for no man desires more of it than he already has. This shows that reason is by nature equal in all men. If there is diversity of opinion, this arises from the fact that we conduct our thought by different ways and consider not the same things. It does not suffice that the understanding be good - it must be well applied.

My mind is no better than another's, but I have been lucky enough to chance on certain ways, which have led me to a certain method by means of which it seems to me that I may by degrees augment my knowledge to the modest measure of my intellect and my length of days. I shall be very glad to make plain in this Discourse the paths I have followed, and to picture my life so that all may judge of it, and by the setting forth of their opinions may furnish me with yet other means of improvement.

It is my design not to teach the method which each man ought to follow for the right guidance of his reason, but only to show in what manner I have tried to conduct my own.

I had been nourished on letters from my infancy, but as soon as I had finished the customary course of study, I found myself hampered by so many doubts and errors that I seemed to have reaped no benefits, except that I had observed more and more of my ignorance. Yet I was at one of the most celebrated schools in Europe, and I was not held inferior to my fellow-students, some of whom were destined to take the place of our masters; nor did our age seem less fruitful of good wits than any which had gone before.

Though I did not cease to esteem the studies of the schools, I began to think that I had given enough time to languages, enough also to ancient books, their stories and their fables; for when a man spends too much time in travelling abroad he becomes a stranger in his own country; and so, when he is too curious concerning what went on in past ages, he is apt to remain ignorant of what is taking place in his own day. I set a high price on eloquence, and I was in love with poetry; I rejoiced in mathematics, but knew nothing of its true use.

I revered our theology, but, since the way to heaven lies open to the ignorant no less than to the learned, and the revealed truths which lead thither are beyond our intelligence, I did not dare to submit them to my feeble reasonings.

In philosophy there is no truth which is not disputed and which, consequently, is not doubtful; the other sciences all borrow their principles from philosophy.

Therefore, I entirely gave up the study of letters and employed the rest of my youth in travelling, being resolved to seek no other science than that which I might find within myself, or in the great Book of the World.

Here the best lesson that I learnt was not to believe too firmly anything of which I had learnt merely by example and custom; and thus little by little was delivered from many errors which are liable to obscure the light of nature and to diminish our capacity of hearing reason. Finally, I resolved one day to study myself in the same way, and in this it seems to me I succeeded much better than if I had never departed from either my country or my books.


BEING in Germany, on my way to rejoin the army after the coronation of the Emperor (Ferdinand II), I was lying at an inn where, in default of other conversation, I was at liberty to entertain my own thoughts. Of these, one of the first was that often there is less perfection in works which are composite than in those which issue from a single hand. Such was the case with buildings, cities, states; for a people which has made its laws from time to time to meet particular occasions will enjoy a less perfect polity than a people which from the beginning has observed the constitution of a far-sighted legislator. This is very certain, that the estate of true religion, which God alone has ordained, must be incomparably better guided than any other.

And again, I considered that as, during our childhood, we had been governed by our appetites and our tutors, which are often at variance, which neither of them perhaps always gave us the best counsel, it is almost impossible that our judgments should be so pure and so solid as they would have been if we had had the perfect use of our reason from the time of our birth and had never been guided by anything else.

Hence, as regarded the opinions that I had received into my belief, I thought that, as a private person may pull down his own house to build a finer, so I could not do better than remove them therefrom in order to replace them by sounder, or, after I should have adjusted them to the level of reason, to establish the same once more.

When I was younger I had studied logic, analytical geometry and algebra. Of these, I found that logic served rather for explaining things we already know; while of geometry and algebra, the former is so tied to the consideration of figures that it cannot exercise the understanding without wearying the imagination, and the latter is so bound down to certain rules and ciphers that it has been made a confused and obscure art which hampers the mind instead of a science which cultivates it. And as a state is better governed which has but few laws, and those strictly observed, I believed that I should find sufficient these four precepts:

THE first was never to accept anything as true when I did not recognize it clearly to be so - that is to say, carefully to avoid precipitation and prejudice, but to include in my opinions nothing beyond that which should present itself so clearly and distinctly to my mind that I might have no occasion to doubt it.

The second was to divide up the difficulties which I should examine into as many parts as possible, and as should be required for their better solution.

The third was to conduct my thoughts in order, by beginning with the simplest objects, so as to mount little by little, by stages, to the most complex knowledge, even supposing an order among things which did not naturally stand in an order of antecedent and consequent.

And the last was to make every where enumerations so complete, and surveys so wide, that I should be sure of omitting nothing.

Exact observation of these precepts gave me such facility in unravelling the questions comprehended in geometrical analysis and in algebra, that in two or three months not only did I find my way through many which I had formerly accounted too hard for me, but, towards the end, I seemed to be able to determine, in those which were new to me, by what means and to what extent it was possible to resolve them.

And so I promised myself that I would apply my system with equal success to the difficulties of other sciences; but since their principles must all be borrowed from philosophy, in which I found no certain principles of its own, I thought that before all else I must try to establish some therein. By way of preparation (for I was then but twenty-three years old) I must root up from my mind my previous bad opinion of it, and must practise my method in order that I might be confirmed in it.


MEANWHILE I must have a rule of life as a shelter while my new house was in building, and this consisted of three or four maxims.

The first was to conform myself to the laws and customs of my country and to hold to the religion in which, by God's grace, I had been brought up; guiding myself, for the rest, by the least extreme opinions of the most intelligent. Among extremes I counted all promises by which a man curtails anything of his liberty; for I should have deemed it a grave fault against good sense if, because I approved something in a given moment, I had bound myself to accept it as good for ever after.

My second maxim was to follow resolutely even doubtful opinions when sure opinions were not available, just as the traveller, lost in some forest, had better walk straight forward, though in a chance direction; for thus he will arrive, if not precisely where he desires to be, at least at a better place than the middle of a forest.

My third maxim was to endeavour always to conquer myself rather than fortune, and to change my desires rather than the order of the world, and in general to bring myself to believe that there is nothing wholly in our power except our thoughts. And I believe that herein lay the secret of those philosophers who, in the days of old, could withdraw from the domination of fortune and, despite pain and poverty, challenge the felicity of their gods.

Finally, after looking out upon the divers occupations of men, I pondered that I could do no better than persevere in that which I had chosen - so deep was my content in discovering every day by its means truths which seemed to me important, yet were unknown to the world.

Having thus made myself sure of these maxims, and having set them apart together with the verities of faith, I judged that for the rest of my opinions I might set freely to work to divest myself of them. For nine years, therefore, I went up and down the world a spectator rather than an actor. These nine years slipped away before I had begun to seek for the foundations of any philosophy more certain, nor perhaps should I have dared to undertake the quest had it not been put about that I had already succeeded.


I HAD long since remarked that in matters of conduct it is necessary sometimes to follow opinions known to be uncertain, as if they were not subject to doubt; but, because now I was desirous to devote myself to the search after truth, I considered that I must do just the contrary, and reject as absolutely false every-thing concerning which I could imagine the least doubt to exist.

Thus, because our senses sometimes deceive us, I would suppose that nothing is such as they make us to imagine it; and because I was as likely to err as another in reasoning, I rejected as false all the reasons which I had formerly accepted as demonstrative; and finally, considering that all the thoughts we have when awake can come to us also when we sleep without any of them being true, I resolved to feign that everything which had ever entered my mind was no more truth than the illusion of my dreams.

But I observed that, while I was thus resolved to feign that everything was false, I who thought must of necessity be somewhat; and remarking this truth - I think, therefore I am - was so firm and so assured that all the most extravagant suppositions of the sceptics were unable to shake it, I judged that I could unhesitatingly accept it as the first principle of the philosophy I was seeking. I could feign that there was no world, I could not feign that I did not exist. And I judged that I might take it as a general rule that the things which we conceive very clearly and very distinctly are all true, and that the only difficulty lies in the way of discerning which those things are that we conceive distinctly.

After this, reflecting upon the fact that I doubted, and that consequently my being was not quite perfected (for I saw that to know is a greater perfection than to doubt), I bethought me to inquire whence I had learnt to think of something more perfect than myself; and it was clear to me that this must come from some nature which was in fact more perfect. For other things I could regard as dependencies of my nature if they were real, and if they were not real they might proceed from nothing - that is to say, they might exist in me by way of defect.

But it could not be the same with the idea of a being more perfect than my own; for to derive it from nothing was manifestly impossible; and because it is no less repugnant that the more perfect should follow and depend upon the less perfect than that something should come forth out of nothing. I could not derive it from myself.

It remained, then, to conclude that it was put into me by a nature truly more perfect than was I and possessing in itself all the perfections of what I could form an idea - in a word, by God. To which I added that, since I knew some perfections which I did not possess, I was not the only being who existed, but that there must of necessity be some other b
ing, more perfect, on whom I depended, and from whom I had acquired all that I possessed; for if I had existed alone and independent of all other, so that I had of myself all this little whereby I participated in the Perfect Being, I should have been able to have in myself all those other qualities which I knew myself to lack, and so to be infinite, eternal, immutable, omniscient, almighty - in fine, to possess all the perfections which I could observe in God.

PROPOSING to myself the geometer's subject matter, and then turning again to examine my idea of a Perfect Being, I found that existence was comprehended in that idea just as in the idea of a triangle is comprehended the notion that the sum of its angles is equal to two right angles; and that consequently it is as certain that God, this Perfect Being is or exists, as any geometrical demonstration could be.

That there are many who persuade themselves that there is a difficulty in knowing Him is due to the scholastic maxim that there is nothing in the understanding which has not first been in the senses; where the ideas of God and the soul have never been.

Than the existence of God all other things, even those which it seems to a man extravagant to doubt, such as his having a body, are less certain. Nor is there any reason sufficient to remove such doubt but such as presupposes the existence of God. From His existence it follows that our ideas or notions, being real things, and coming from God, cannot but be true in so far as they are clear and distinct. In so far as they contain falsity, they are confused and obscure, there is in them an element of mere negation (elles participent du neant); that is to say, they are thus confused in us because we ourselves are not all perfect. And it is evident that falsity or imperfection can no more come forth from God than can perfection proceed from nothingness. But, did we not know that all which is in us of the real and the true comes from a perfect and infinite being, however clear and distinct our ideas might be, we should have no reason for assurance that they possessed the final perfection - truth.

Reason instructs us that all our ideas must have some foundation of truth, for it could not be that the All-Perfect and the All-True should otherwise have put them into us; and because our reasonings are never so evident or so complete when we sleep as when we wake, although sometimes during sleep our imagination may be more vivid and positive, it also instructs us that such truth as our thoughts have will be in our waking thoughts rather than in our dreams.


I HAVE always remained firm in my resolve to assume no other principle than that which I have used to demonstrate the existence of God and of the soul, and to receive nothing which did not seem to me clearer and more certain than the demonstrations of the philosophers had seemed before; yet not only have I found means of satisfying myself with regard to the principal difficulties which are usually treated of in philosophy, but also I have remarked certain laws which God has so established in nature, and of which He has implanted such notions in our souls, that we cannot doubt that they are observed in all which happens in the world.

The principal truths which flow from these I have tried to unfold in a treatise (On the World, or on Light), which certain considerations prevent me from publishing. This I concluded three years ago, and had begun to revise it for the printer, when I learnt that certain persons to whom I defer had disapproved an opinion on physics published a short time before by a certain person (Galileo), in which opinion I had noticed nothing prejudicial to religion; and this made me fear that there might be some among my opinions in which I was mistaken.

I now believe that I ought to continue to write all the things which I judge of importance, but ought in no wise to consent to their publication during my life. For my experience of the objections which might be made forbids me to hope for any profit from them. I have tried both friends and enemies, yet it has seldom happened that they have offered any objection which I had not in some measure foreseen; so that I have never, I may say, found a critic who did not seem to be either less rigorous or less fair-minded than myself.

Whereupon I gladly take this opportunity to beg those who shall come after us never to believe that the things which they are told come from me unless I have divulged them myself; and I am in nowise astonished at the extravagances attributed to those old philosophers whose writings have not come down to us. They were the greatest minds of their time, but have been ill reported.

Why, I am sure that the most devoted of those who now follow Aristotle would esteem themselves happy if they had as much knowledge of nature as he had, even on the condition that they should never have more! They are like ivy, which never mounts higher than the trees which support it, and which even comes down again after it has attained their summit. So at least, it seems to me, do they who, not content with knowing all that is explained by their author, would find in him the solution also of many difficulties of which he says nothing, and of which, perhaps, he never thought.

Yet their method of philosophising is very convenient for those who have but middling minds, for the obscurity of the distinctions and principles which they employ enables them to speak of all things as boldly as if they had knowledge of them, and sustain all they have to say against the most subtle and skilful without there being any means of convincing them; wherein they seem to me like a blind man who, in order to fight on equal terms with a man who has his sight, invites him into the depths of a cavern.

And I may say that it is to their interest that I should abstain from publishing the principles of the philosophy which I employ, for so simple and so evident are they that to publish them would be like opening windows into their caverns and letting in the day. But if they prefer acquaintance with a little truth, and desire to follow a plan like mine, there is no need for me to say to them any more in this discourse than I have already said.

For if they are capable of passing beyond what I have done, much rather will they be able to discover for themselves whatever I believe myself to have found out; besides which, the practice which they will acquire in seeking out easy things and thence passing to others which are more difficult, will stead them better than all my instructions.

But if some of the matters spoken about at the beginning of the Dioptrics and the Meteors (published with the Discourse on Method) should at first give offence because I have called them 'suppositions,' and have shown no desire to prove them, let the reader have patience to read the whole attentively, and I have hope that he will be satisfied.

The time remaining to me I have resolved to employ in trying to acquire some knowledge of nature, such that we may be able to draw from it more certain rules for medicine than those which we possess. And I hereby declare that I shall always hold myself more obliged to those by whose favour I enjoy my leisure undisturbed than I should be to any who should offer me the most esteemed employments in the world.

René Descartes
Descrates' memorial in the Adolf Fredrik Kyrkogård in Stockholm,
his remains were later removed to Paris

ISBN 9781326806781
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