24th June 2026
THE SEARCH FOR TRUTH BY MEANS OF THE NATURAL LIGHT – Descartes
La Recherche de la Write par la lumiere naturelle
This light alone, without any help from religion or philosophy, determines what opinions a good man should hold on any matter that may occupy his thoughts, and penetrates into the secrets of the most recondite sciences.
A good man is not required to have read every book or diligently mastered everything taught in the Schools. It would, indeed, be a kind of defect in his education if he had spent too much time on hook-learning. Having many other things to do in the course of his life, he must judiciously measure out his time so as to reserve the better part of it for performing good actions — the actions which his own reason would have to teach him if he learned everything from it alone. But he came into the world in ignorance, and since the knowledge which he had as a child was based solely on the weak foundation of the senses and the authority of his teachers, it was virtually inevitable that his imagination should be filled with innumerable false thoughts before reason could guide his conduct. So later on he needs to have very great natural talent, or else the instruction of a wise teacher, in order to rid himself of the bad doctrines that have filled his mind, to lay the foundations for a solid science, and to discover all the ways in which he can raise his knowledge to the highest level that it can possibly attain.
I intend in this work to explain these matters. I shall bring to light the true riches of our souls, opening up to each of us the means whereby we can find within ourselves, without any help from anyone else, all the knowledge we may need for the conduct of life, and the means of using it in order to acquire all the most abstruse items of knowledge that human reason is capable of possessing.
But in case the grandeur of my plan should immediately fill your minds with so much wonder as to leave no room for belief, I must tell you that what I am undertaking is not so difficult as one might imagine. For the items of knowledge that lie within reach of the human mind are all linked together by a bond so marvellous, and can be derived from each other by means of inferences so necessary, that their discovery does not require much skill or intelligence — provided we begin with the simplest and know how to move stage by stage to the most sublime. In what follows I shall try to explain this by means of a chain of reasoning which is so clear and accessible to all that anybody who has not reached the same conclusions earlier will blame his failure to do so simply on the fact that he did not cast his eyes in the right direction and fix his thoughts on the matters that I considered. And I shall not deserve any more glory for having made these discoveries than a passer-by would deserve for having accidentally stumbled upon some rich treasure for which many persons had previously conducted a diligent but unsuccessful search.
I am surprised, indeed, that amongst so many exceptional minds, much better equipped than I to carry out this task, none have had the patience to pick their way through the difficulties. Instead they have nearly all acted like travellers who leave the main path to take a shortcut, only to find themselves lost amongst briars and precipices.
But I do not wish to consider what others have known or not known. I am content to observe that even if all the knowledge that can be desired were contained in books, the good things in them would be mingled with so many useless things, and scattered haphazardly through such a pile of massive tomes, that we should need more time for reading them than our present life allows, and more intelligence for picking out the useful material than would be required for discovering it on our own.
This makes me hope that you will be happy to find here an easier path. I hope too that the truths I set forth will not be any less well received for their not being derived from Aristotle or Plato, and that they will have currency in the world in the same way as money, whose value is no less when it comes from the purse of a peasant than when it comes from a bank. Moreover I have done my best to make these truths equally useful to everybody. I could find no style better suited to this end than that of a conversation in which several friends, frankly and without ceremony, disclose the best of their thoughts to each other. Thus let us imagine that Eudoxus, a man of moderate intellect but possessing a judgement which is not corrupted by any false beliefs and a reason which retains all the purity of its nature, is visited in his country home by two friends whose minds are among the most outstanding and inquiring of our time. One of them, Polyander, has never studied at all, while the other, Epistemon, has a detailed knowledge of everything that can be learned in the Schools. Leaving to your imagination their other conversations as well as their surroundings (from which, however, I shall frequently have them take examples in order to make their thoughts clearer), I shall now present them introducing the topic which will occupy them throughout these two books.
Polyander I consider you very fortunate to have found all those fine things in the Greek and Latin literature. Indeed, it seems to me that if I had studied as much as you, I should have been as different from my present self as the angels are from you. I cannot forgive the folly of my parents for believing that the pursuit of learning enfeebles the spirit, and for sending me to court and into the army at such an early age, and I shall regret my ignorance for the rest of my life if I do not learn anything through my association with you.
Epistemon The best thing I can tell you on this topic is that the desire for knowledge, which is common to all men, is an illness which cannot be cured, for curiosity grows with learning. But because the defects in the soul trouble a person only in so far as he becomes aware of them, you have an advantage over us in that, unlike us, you do not notice all the many things which you lack.
Eudoxus Is it possible, Epistemon, that you, with all your learning, are persuaded that nature can contain a malady so universal without also providing a remedy for it? For my part, just as I think that each land has enough fruits and rivers to satisfy the hunger and thirst of all its inhabitants, so too I think that enough truth can be known in each subject to satisfy amply the curiosity of orderly souls. The body of a person suffering from dropsy is no further removed from its proper condition than is the mind of someone who is perpetually tormented by an insatiable curiosity.
Epistemon I have, indeed, heard that our desire cannot naturally extend to matters which appear to us to be impossible, and that it ought not to extend to those which are evil or useless. But there are so many things to be known which seem to us possible and which are not only good and pleasant but also very necessary for the conduct of our actions; and I cannot believe that anyone ever knows so much that he cannot have good reasons to desire to know more.
Eudoxus What will you say of me, then, if I assure you that I no longer feel any passion to learn anything at all. I am as happy with what little knowledge I have as ever Diogenes was in his barrel, and this without having any need for his philosophy.[1] For my neighbours’ knowledge does not limit mine in the way that their fields form the boundaries of my small property. And my mind, having at its disposal all the truths it comes across, does not dream there are others to discover. Instead it enjoys the same tranquillity as would a king if his country were so isolated and cut off from others that he imagined there was nothing beyond his frontiers but infertile deserts and uninhabitable mountains.
Epistemon If anyone else were to speak to me in this manner, I should consider him to be very vain or else to be lacking in curiosity. But you escape the charge of vanity because you have chosen to retire to this remote place and because you are so unconcerned about being well known; and in view of the time you formerly spent in travelling, in associating with learned men, and in investigating all the most complex discoveries in every science, we can be sure that you do not lack curiosity. So all I can say is that I consider you extremely happy, and I am convinced that you must therefore be in possession of knowledge which is far more perfect than that enjoyed by others.
Eudoxus I thank you for the good opinion you hold of me. But I would not presume so much upon your courtesy as to expect you simply to take my word for what I have said. One must never advance propositions so soz remote from common opinion without at the same time being able to point out some of their consequences. That is why I invite you both to stay here this summer, so that I may have time to show you a part of what I know. For I venture to hope not only that you will admit that I have some reason for being content with my knowledge, but, in addition, that you for your part will be fully satisfied with the things you have learned.
Epistemon I have no hesitation in accepting a kindness which I was myself going to beg of you.
Polyander For my part, I shall be pleased to be present at this discussion, though I do not think myself capable of deriving any profit from it.
Eudoxus On the contrary, Polyander, I think it is you who will gain the greater benefit from it, since you are unprejudiced; and it will be far easier for me to set on the right track someone who is neutral than to guide Epistemon, who will often take up the opposite position. But to give you a more distinct conception of the sort of doctrine I propose to teach, I should like you to notice how the sciences differ from those simple forms of knowledge which can be acquired without any process of reasoning, such as languages, history, geography and in general any subject which rests on experience alone. I readily grant that one man could not live long enough to acquire first-hand experience of everything in the world; but I am no less convinced that it would be folly to desire 503 this. A good man is not required to know Greek or Latin any more than the languages of Switzerland or Brittany, or the history of the Empire any more than that of the smallest state in Europe. He ought simply to take care to employ his leisure in good and useful occupations, and equip his memory only with the most necessary knowledge. As to the sciences —which are simply a matter of our making reliable judgements on the basis of knowledge we already possess — some are drawn from ordinary facts about which everyone has heard, and others from observations which are unusual and highly contrived. I admit, too, that we could not possibly discuss each of the latter in detail. For we should need first of all to have examined all the herbs and stones that come from the Indies, to have beheld the Phoenix, and in short to have knowledge of all the marvels of nature. But I believe I shall adequately fulfil my promise if I explain to you the truths which can be deduced from the ordinary facts known to each of us, and so make you capable of discovering for yourselves all the others, when you care to take the trouble to look for them.
Polyander I think that this is all we can possibly desire. I should be happy if you would merely prove a certain number of propositions which are so well known that no one is ignorant of them, such as those concerning the Deity, the rational soul, the virtues and their rewards, etc. I compare these propositions to those ancient families which everyone recognizes as being very illustrious even though their titles to nobility lie buried in the ruins of antiquity. For I have no doubt at all that those who first brought mankind to believe these truths were able to prove them with very strong arguments. But ever since that time, these proofs have been repeated so rarely that no one knows them any longer. These truths are so important, however, that prudence obliges us to believe them blindly at the risk of being mistaken, rather than to wait until the next world in order to get clear about them.
Epistemon For my part, I am a little more curious, and I should like you to go on to clarify for me some special difficulties which I find in every science, and chiefly those concerning human contrivances, apparitions, illusions, and in short all the marvellous effects attributed to magic. For I think it is useful to know about them, not in order to make use of them, but in order to prevent our judgement from being beguiled by wonder at something of which it is ignorant.
Eudoxus I shall try to satisfy both of you. In order to establish an order that we can follow to the end, first of all, Polyander, I should like us to have a discussion, just the two of us, about all the things in the world, considering them as they are in themselves. I want Epistemon to interrupt as little as possible, because his objections would often force us to depart from our subject. Afterwards we shall all consider these things afresh, but under a different aspect, namely in so far as they are related to us and can be described as true or false, and good or bad. It is here that Epistemon will have a chance to set forth all the difficulties which will have occurred to him during the preceding conversations.
Polyander Tell us the order, then, that you will follow in your explanations.
Eudoxus We must begin with the rational soul, for ail our knowledge resides in it; and after considering its nature and effects, we shall proceed to its author. When we have come to know who he is, and how he has created all things that exist in the world, we shall be able to see what is most certain regarding the other creatures, and we shall examine in what way our senses receive their objects and how our thoughts are made true or false. Then I shall lay before your eyes the works of men involving corporeal things. After causing you to wonder at the most powerful machines, the most unusual automatons, the most impressive illusions and the most subtle tricks that human ingenuity can devise, I shall reveal to you the secrets behind them, which are so simple and straightforward that you will no longer have reason to wonder at anything made by the hands of men. I shall then pass to the works of nature, and after showing you the cause of all her changes, the variety of her qualities, and how the souls of plants and of animals differ from ours, I shall present for your 5o6 consideration the entire edifice of the things that are perceivable by the senses. After giving an account of celestial phenomena and what we can judge with certainty about them, I shall pass on to the soundest conjectures concerning matters which cannot be definitely settled by men, in order to explain the relation of things perceivable by the senses to things perceivable by the intellect, the relation of both sorts of things to the Creator, the immortality of his creatures, and their state of being after the end of time. Then we shall come to the second part of this discussion, where we deal with each science in particular, picking out the most solid elements in each of them and proposing the method for carrying them much further forward than has hitherto been achieved — a method which enables someone of average intelligence to discover for himself everything that the most subtle minds can devise. Having thus prepared our understanding to make perfect judgements about the truth, we must also learn to control our will by distinguishing good things from bad, and by observing the true difference between virtues and vices. That done, I trust that your passion for knowledge will not be so intense, and that it will seem to you that everything I have said has been satisfactorily proved —so much so that you will believe that a man with a good mind, even one brought up in a desert and never illuminated by any light but the light of nature, could not have opinions different from ours if he carefully weighed all the same reasons. Now, to enter upon this discussion, we must ask the following questions: What are the first things that people know? What part of the soul does this knowledge reside in? And why is it 507 so imperfect to begin with?
Epistemon It seems to me that all this can be explained very clearly if we compare the imagination of a child to a tabula rasa on which our ideas are to be traced, these ideas being like portraits drawn from nature. Our senses, inclinations, teachers and intellect are the different artists who may work at this task, and among them the least competent are the first to take part, namely our imperfect senses, blind instincts and foolish nurses. The most competent is the intellect, which comes last; and it must serve an apprenticeship of many years, following the example of its masters for a long time before daring to correct any of their errors. In my opinion, this is one of the chief causes of the difficulties we have in acquiring knowledge. For our senses see nothing beyond the more coarse and ordinary things and our natural inclinations are entirely corrupt; and as to our teachers, although undoubtedly you might find very perfect ones among them, they cannot force our judgement to accept their reasonings until our intellect has done the work (which only it can do) of examining them. But the intellect is like an excellent painter who is called upon to put the finishing touches to a bad picture sketched out by a young apprentice. It would be futile for him to employ the rules of his art in correcting the picture little by little, a bit here and a bit there, and in adding with his own hand all that is lacking in it, if, despite his best efforts, he could never remove every major fault, since the drawing was badly sketched from the beginning, the figures badly placed, and the proportions badly observed.
Eudoxus Your comparison nicely illustrates the first obstacle facing us; but you do not describe the means we must use if we wish to avoid it. Now it seems to me that your painter would do far better to make a fresh start on the picture; rather than wasting time in correcting all the lines he finds on the canvas, he should wipe them off it with a sponge. Similarly, as soon as a man reaches what we call the age of discretion he should resolve once and for all to remove from his imagination all traces of the imperfect ideas which have been engraved there up till that time. Then he should begin in earnest to form new ideas, applying all the strength of his intellect so effectively that if he does not bring these ideas to perfection, at least he will not be able to blame the weakness of the senses or the irregularities of nature.
Epistemon That would be an excellent remedy if it were easy to apply. But you are not ignorant of the fact that the opinions first received in our imagination remain so deeply imprinted there that our will cannot erase them on its own, but can do so only by calling on the assistance of powerful reasons.
Eudoxus I should like to try and impart some of these reasons to you. But if you wish to derive any profit from this conversation, you must now give me your attention, and let me converse a bit with Polyander; this will enable me to begin by overturning all the knowledge acquired up to the present. For, since this knowledge is not enough to satisfy him, it must be faulty: I would compare it to a badly constructed house, whose foundations are not firm. I know of no better way to repair it than to knock it all down, and build a new one in its place. For I do not wish to be one of those jobbing builders who devote themselves solely to refurbishing old buildings because they consider themselves incapable of undertaking the construction of new ones. But, Polyander, while engaged upon this work of demolition we can use the same method to dig the foundations which ought to serve our purpose, and to prepare the best and most solid materials which will be needed for building up these foundations. So please join me in considering which, of all the truths men can know, are the most certain and the easiest to become acquainted with.
Polyander Is there anyone who can doubt that things that are perceivable by the senses — by which I mean those which can be seen and touched — are much more certain than all the others? I for one would be quite astonished if you were to make me see just as clearly any of the things which are said about God or the soul.
Eudoxus That is just what I hope to do. I find it strange that men are so credulous as to base their knowledge on the certitude of the senses, when everyone knows that they are sometimes deceptive, and that we have good reason always to distrust those who have deceived us even once.
Polyander I am well aware that the senses are sometimes deceptive if they are in poor condition, as when all food seems bitter to a sick person; or if their objects are too far away, as when we look at the stars, which never appear so large to us as they really are; or, in general, whenever they do not act freely in accordance with their natural constitution. But such defects of the senses are all quite easy to recognize, and do not prevent me from being quite sure at present that I am seeing you, that we are walking in this garden, that the sun is shining on us, and in a word, that everything which ordinarily appears to my senses. is genuine.
Eudoxus So if I wish to make you fear that the senses are deceptive on occasions when you are unaware of the deception, it is not enough for me to tell you that the senses deceive you on certain occasions when you perceive the deception. I shall have to go further, and ask if you have never seen one of those melancholic individuals who think themselves to be vases, or take some part of their body to be enormous; they will swear that what they see and touch is just as they imagine it to be. To be sure, a good man would be indignant if you told him that his beliefs cannot have any more rational basis than theirs, since he relies, like them, on what the senses and imagination represent to him. But you cannot take it amiss if I ask whether you are not, like all men, liable to fall asleep, and whether you cannot think, while asleep, that you are seeing me, that you are walking in this garden, that the sun is shining — in brief, all the things of which you now believe you are utterly certain. Have you never heard this expression of astonishment in comedies: ‘Am I awake or asleep?’ How can you be certain that your life is not a continuous dream, and that everything you think you learn through your senses is not false now, just as much as when you are asleep? In particular, how can you be certain of this when you have learned that you were created by a superior being who, being all-powerful, would have found it no more difficult to create us just as I am describing, than to create us as you think you are?
Polyander There, surely, we have arguments sufficient to overturn all the teachings of Epistemon, if he is reflective enough to give his attention to them. For myself, however, I fear that I should simply go wool gathering if I tried to consider such abstract matters, for I am a man who has never engaged in study or accustomed himself to turning his mind so far away from things that are perceivable by the senses.
Epistemon I agree that it is very dangerous to proceed too far in this line of thinking. Such general doubts would lead us straight into the ignorance of Socrates or the uncertainty of the Pyrrhonists.[2] These are deep waters, where I think we may lose our footing.
Eudoxus I confess that it would be dangerous for someone who does not know a ford to venture across it without a guide, and many have lost their lives in doing so. But you have nothing to fear if you follow me.
Indeed, just such fears have prevented most men of letters from acquiring a body of knowledge which was firm and certain enough to deserve the name ‘science’[3]. Supposing that there was no firmer basis for their opinions other than things perceivable by the senses, they have built upon sand instead of digging further down to find rock or clay. So we must not let the matter rest here, especially since even if you did not wish to give further consideration to the arguments I have stated, the arguments have already done what I desired: their chief effect has been to touch your imagination so as to make you fear them. For this indicates that your knowledge is not so infallible as to prevent your fearing that these arguments will undermine its foundations by making you doubt everything. Consequently it indicates that you already have these doubts, and so I have achieved my aim, which was to overturn all your learning by showing you its uncertainty. But in case you should now lack the courage to proceed any further, I would advise you that these doubts, which alarmed you at the start, are like phantoms and empty images which appear at night in the uncertain glimmer of a weak light: if you flee from them, your fear will follow you, but if you approach as if to touch them, you will find nothing but air and shadow and you will be more confident the next time such an encounter may occur.
Polyander I should like, then, to follow your suggestion and set forth these difficulties in the strongest form possible. I shall apply my mind to the task of doubting whether I have not been dreaming all my life, and whether all the ideas I thought capable of entering my mind only by way of the senses were not in fact formed by themselves, just as similar ideas are formed whenever I am asleep, and I know that my eyes are shut, my ears closed, and in short, that none of my senses help to form them. Thus I shall be uncertain not only about whether you are in the world and whether there is an earth or a sun; but also about whether I have eyes, ears, a body, and even whether I am speaking to you and you are speaking to me. In short, I shall doubt everything.[4]
Eudoxus There you are, all prepared, and at the very stage to which I had intended to bring you. The time has now come for you to consider closely the conclusions which I wish to draw at this point. Now, you see that you can reasonably have doubts about everything that you know only by means of the senses. But can you ever have doubts about your doubt, and remain doubtful whether you are doubting or not?
Polyander I must confess that your question strikes me with amazement. The modicum of insight I possess (which gives me a moderate amount of good sense) makes me see with some astonishment that I am forced to confess that I know nothing with any certainty, that I am doubtful about everything and certain of nothing. But what do you want to infer from this? I do not see that this universal amazement can be of any use, nor do I see how this sort of doubt can be a principle which gets us very far. For you arranged this conversation with quite the opposite end in view — to free us from our doubts and make clear to us truths which we should know and which even Epistemon, for all his learning, might not know.
Eudoxus Just give me your attention and I shall conduct you further than you think. For from this universal doubt, as from a fixed and immovable point, I propose to derive the knowledge of God, of yourself, and of everything in the universe.
Polyander You are promising a great deal indeed; and if things turn out as you promise, it will be worth our while to grant your initial demands. Keep your word and we shall be quite content to do so.
Eudoxus You cannot deny that you have such doubts; rather it is certain that you have them, so certain in fact that you cannot doubt your doubting. Therefore it is also true that you who are doubting exist; this is so true that you can no longer have any doubts about it.
Polyander I quite agree with you on that point, because if I did not exist, I would not be able to doubt.
Eudoxus You exist, therefore, and you know that you exist, and you know this just because you are doubting.
Polyander All of this is quite true.
Eudoxus But, so that you are not deflected from the course I suggested, let us proceed gradually, and as I said, you will find that you are making greater progress than you think. Let us go through the argument again. You exist, and you know that you exist, and you know this because you know that you are doubting. But what are you — you who have doubts about everything but cannot doubt that you yourself exist?
Polyander The answer to that is not at all difficult, and I can see perfectly well why you chose me rather than Epistemon to answer your questions: you did not want to ask anything which could not be answered very easily. So I shall say I am a man.
Eudoxus You are not paying attention to my question, and the reply you give me, however simple it may seem to you, would plunge you into very difficult and complicated problems, were I to press you even a little. If, for example, I were to ask even Epistemon himself what a man is, and he gave the stock reply of the scholastics, that a man is a ‘rational animal’, and if, in order to explain these two terms (which are just as obscure as the former), he were to take us further, through all the levels which are called ‘metaphysical’, we should be dragged into a maze from which it would be impossible to escape. For two other questions arise from this one. First, what is an animal? Second, what is rational? If, in order to explain what an animal is, he were to reply that it is a ‘living and sentient being’, that a living being is an ‘animate body’, and that a body is a ‘corporeal substance’, you see immediately that the questions, like the branches of a family tree, would rapidly increase and multiply. Quite clearly, the result of all these admirable questions would be pure verbiage, which would elucidate nothing and leave us in our original state of ignorance.
Epistemon I am sorry you despise the tree of Porphyry,[5] which the learned have always admired, and it annoys me that you would try to convey to Polyander what he is in a different way from the one which has long been universally accepted in the Schools. To this day no better or more appropriate way has been found for explaining what we are than displaying all the levels which make up our whole nature, for in this way, by passing up and down through all these levels, we can learn what our nature has in common with the natures of all other things, and in what respects it differs from them. And this is the highest point to which our knowledge can reach.
Eudoxus I have never had any intention of condemning the method of explanation ordinarily employed in the Schools, nor shall I ever wish to. For it is to that method that I owe the little I know, and my use of it has helped me to recognize the uncertainty of all the things I have learned there. So, even if my teachers taught me nothing that was certain, I owe them my thanks none the less, since it was due to their instruction that I came to realize this. Indeed, the fact that everything they taught me was quite doubtful gives me greater reason now to be thankful than would have been the case had their teaching been in closer accord with reason; for in the latter case I might have been content with the smattering of reason which I found in it, and that might have made me less conscientious in searching carefully for the truth. What I told Polyander serves not so much to point out to him the confusion and uncertainty into which his answer plunges you as to make him more attentive in future to my questions. Thus I am addressing my remarks to him; and to keep us from wandering any further from our path, I ask him once more what he is — he who can have doubts about everything but cannot have doubts about himself.
Polyander I thought I had satisfied you when I said that I am a man, but I quite see that I misread the situation: I can see that my answer does not satisfy you, and I must admit that it no longer seems adequate to me, especially when I think of the confusion and uncertainty into which, as you have shown me, it can plunge us if we want, to make the answer clearer and understand it better. Indeed, whatever Epistemon may say, it strikes me that there is a great deal of obscurity in these metaphysical levels. If, for example, we say that a body is a ‘corporeal substance’, without making clear what a corporeal substance is, these two words do not tell us any more than does the word ‘body’. In the same way, if we assert that to be living is to be an ‘animate body’, without first explaining what a body is and what it is to be animate — and likewise with all the other metaphysical levels — we are uttering words and putting them as it were in a certain order, but we are not really saying anything. The words do not convey anything that can be conceived, or form any distinct idea in our mind. When, in reply to your question, I said that I was a man, I was not actually thinking of all the scholastic entities which I knew nothing about and had never heard of, and which, so far as I am concerned, subsist only in the imagination of those who have invented them. I was thinking, rather, about the things we see, touch, perceive with our senses, and experience within ourselves — in a word, about things which even the most simple-minded of men know just as well as the greatest philosopher in the world. Undoubtedly I am a certain whole made up of two arms, two legs, one head, and all the other parts which make up what we call the human body, and which besides is nourished, walks, perceives by the senses, and thinks.
Eudoxus I saw at once from your answer that you had not properly understood my question, and that you answered more questions than I had asked. Now, in the list of things which you were doubting earlier on, you had already included arms, legs, head, and all the other parts which make up the mechanism of the human body. It was not my intention to question you about these things, the existence of which you are not certain of. Tell me, then, what you are, strictly speaking, in so far as you are doubting. This was the sole point on which I had decided to question you, because beyond this you can know nothing for certain.
Polyander I now see that I was mistaken in my answer, and that I went much further than was appropriate, since I did not quite grasp your intention. This will make me more careful in future, and it makes me marvel now at the precision of your method, as you guide us step by step along simple and easy paths towards knowledge of the things you want to teach us. But we have reason to say that it was a happy mistake I made, since, thanks to it, I know very well that what I am, in so far as I am doubting, is certainly not what I call my body. Indeed, I do not even know whether I have a body; you have shown me that it is possible to doubt it. I might add that I cannot deny absolutely that I have a body. Yet even if we keep all these suppositions intact, this will not prevent me from being certain that I exist. On the contrary, these suppositions simply strengthen the certainty of my conviction that I exist and am not a body. Otherwise, if I had doubts about my body, I would also have doubts about myself, and I cannot have doubts about that. I am absolutely convinced that I exist, so convinced that it is totally impossible for me to doubt it.
Eudoxus Splendidly put! So admirably are you acquitting yourself here that I could not put the point better myself. All I need do, I see, is to leave you to get on with the job on your own, after taking care to set you on your course. Provided we have proper direction, all we need for discovering the truth on the most difficult issues is, I think, common sense, to give it its ordinary name. Since, as I had hoped, you have a decent supply of that, I am simply going to point out to you the way you should take in future. Just keep going and, relying on your own resources, draw the conclusions which follow from that first principle.
Polyander This principle seems so fertile, and suggests to me so many things at once that I think I would have an enormous job arranging them in order. Just now you advised me to ponder on what I am, I who am doubting, and not to confuse this with what I once believed myself to be. This single piece of advice has flooded my mind with light and all at once scattered the darkness; so much so that by the light of this torch I see more sharply within myself that which is hidden within me, and I am more convinced that I possess something non-tangible than I ever was that I possessed a body.
Eudoxus I am quite delighted with this sudden enthusiasm, though Epistemon may not be quite so pleased. You have not freed him from his mistake, and you have not placed before his eyes a fraction of the things you say are contained in this principle. So he will always be wondering why he should not believe or at any rate fear that everything which this light presents to you is like a will-o’-the-wisp which dies out and vanishes as soon as you try to get near it, and that you will soon slip back into the darkness you were in before, that is, into your original state of ignorance. It would certainly be an extraordinary occurrence if you, who have never spent much time studying or delving into the works of the philosophers, should so suddenly and so effortlessly end up a learned man. Therefore we should not be surprised that Epistemon thinks the way he does.
Epistemon I admit I took Polyander’s reaction to be a sort of burst of enthusiasm. Polyander has never given much thought to the grand truths which philosophy conveys, and I thought he was so transported by his reflection on the most insignificant of these truths that he could not refrain from displaying his intense excitement to you. But those who, like you,[6] have been plodding this path for a long time, expending much oil and effort in reading and re-reading the writings of the ancients, unravelling the thorniest knots in philosophy, are no longer surprised by such bursts of enthusiasm. They make no more of it than they do of the vain hopes of some who have just begun to learn mathematics. No sooner have such novices been given the line and the circle, and shown what a straight line is and what a curved, than they believe that they are going to discover how to square the circle and duplicate the cube.[7] But we have frequently refuted the views of the Pyrrhonists, and the fruits which they themselves have derived from their philosophical method have been so meagre that they have been wandering about aimlessly all their lives. Unable to free themselves from the doubts which they themselves introduced into philosophy, they have put their efforts exclusively into learning to doubt. So, with all due respect to Polyander, I doubt whether he himself can derive anything better from it.
Eudoxus I quite see that in directing your words to Polyander you want to spare me. Nevertheless it is perfectly obvious that your jests are directed at me. But let Polyander speak, and we shall then see which of us has the last laugh.
Polyander I shall do so gladly. But I fear that the dispute between you two will become heated, and that while you are pursuing the matter at all too exalted a level, I shall not understand any of it, and shall lose all the fruits I am going to reap (I promise myself) when I proceed to retrace my first steps. So I ask Epistemon to let me indulge this hope so long as it pleases Eudoxus to lead me by the hand along the path on which he set me.
Eudoxus Very well; when you consider yourself simply in so far as you are doubting, you realize that you are not a body, and that so considered, none of the parts which make up the mechanism of the human body are to be found within you, that is, you have no arms, legs, head, eyes, ears or any sense organs. But see whether you can reject in the same way all the other things which you previously understood to be implied in your former notion of a man. As you rightly remarked, it was a fortunate error you made when your answer went beyond the bounds of my question. For it makes it easy for you to get to know what you are: all you need do is to separate from yourself and reject everything which you clearly see does not belong to you, and admit only what necessarily belongs to you —so necessarily that you are as certain and convinced of it as you are of your existing and doubting.
Polyander I am grateful to you for setting me on my way in the manner you did; for I no longer knew where I was. I said previously that I was a whole put together with arms, legs, a head and all the parts which make up what is called ‘the human body’, and in addition that I walk, am nourished, perceive by the senses, and think. In order to think of myself simply as I know myself to be, it was also necessary for me to set aside all the parts or components which make up the mechanism of the human body, that is, to think of myself as lacking arms, legs, head — in a word, as lacking a body. And yet it is true that whatever it is within me that is doubting, it is not what I call my body. Therefore it is also true that I, in so far as I am doubting, am not that which is nourished or walks; for neither of these actions can be performed without a body. I cannot even say that I, in so far as I am doubting, am capable of perceiving by the senses. For as feet are needed for walking, so eyes are needed for seeing, and ears for hearing; yet since I have none of these organs — because I have no body — I cannot say I perceive by the senses. Furthermore, in the past I have thought while dreaming that I perceived by the senses many things which I did not really perceive. And since I have decided to admit nothing here unless its truth is such that I can have no doubts about it, I cannot say that I am a sentient being, i.e. one which sees with its eyes and hears with its ears. For it is possible in the way just described that I believe I am perceiving by the senses, even though I have no senses.
Eudoxus I cannot but stop you here, not to lead you off the road but to encourage you and make you consider what good sense can achieve if given proper direction. For is there anything in what you have said which is not exact, which is not validly argued, which is not correctly deduced from what has gone before? All these points have been stated and worked out not by means of logic, or a rule or pattern of argument, but simply by the light of reason and good sense. When this light operates on its own, it is less liable to go wrong than when it anxiously strives to follow the numerous different rules, the inventions of human ingenuity and idleness, which serve more to corrupt it than render it more perfect. Epistemon himself seems to agree with us on this point; for his silence indicates that he agrees entirely with what you have been saying. Go on, then, Polyander, and show him how far we can get with good sense, and also what conclusions can be derived from our first principle.
Polyander Of all the attributes I once claimed as my own there is only one left worth examining, and that is thought. I find that it alone is such that I cannot detach it from myself. For if it is true that I am doubting (I cannot doubt that), it is equally true that I am thinking, for what is doubting if not thinking in a certain kind of way? Indeed, if I did not think at all, I could not know whether I doubted or even existed. But I exist, and I know what I am, and I know these facts because I am doubting, i.e. because I am thinking. It could even happen that, if I were to cease thinking for a moment, I would also completely cease to exist. So the one thing which I cannot separate from myself, and which I know for certain that I am, and which I can now assert with certainty without fear of being mistaken, that one thing, I say, is that I am a thinking thing.
Eudoxus Epistemon, what do you think of what Polyander has just been saying? Do you find, anything in his whole argument which is defective, or anything inconsistent? Would you have thought that an uneducated man who had never bothered to study could reason with such precision, and be so consistent in all his arguments? If I am not mistaken, you must, as a result of this, begin to see that if you simply know how to make proper use of your own doubt, you can use it to deduce facts which are known with complete certainty — facts which are even more certain and more useful than those which we commonly build upon that great principle, as the basis to which they are all reduced, the fixed point on which they all terminate, namely, ‘It is impossible that one and the same thing should exist and at the same time not exist.’ Perhaps I shall have occasion to demonstrate the usefulness of doubt to you. But let us not interrupt the thread of Polyander’s remarks, or stray from the argument. So see whether you have anything to say or any objection to make.
Epistemon Since you are asking me, even needling me, to take sides, I am going to show you what Logic can do when roused, and I shall raise such stiff obstacles that not only Polyander but even you will find it exceedingly difficult to get round them. So rather than going any further, let us stop here and take the trouble to make a rigorous examination of your fundamental principles and conclusions. With the aid of the true Logic and on the basis of your own principles, I shall demonstrate that nothing Polyander has said has a legitimate basis or leads to any firm conclusions. You say that you exist and you know you exist, and you know this because you are doubting and because you are thinking. But do you really know what doubting or what thinking is? Since you do not want to admit anything about which you are not certain or of which you do not have perfect knowledge, how can you be so sure that you exist, on the slender basis of such obscure facts as these? You should really have taught Polyander first of all what doubt is, what thought is, what existence is, so that his reasoning might have the strength of a demonstration, and that he might understand himself before trying to make himself intelligible to others.
Polyander That is quite beyond me; so I shall give up the struggle and leave you and Epistemon to unravel this knot together.
Eudoxus I shall undertake the task with pleasure on this occasion, but only on condition that you act as judge in our dispute, for I dare not hope that Epistemon will give in to my arguments. Someone who, like him, is stuffed full of opinions and taken up with any number of preconceptions finds it difficult to submit himself exclusively to the natural light, for he has long been in the habit of yielding to authority rather than lending his ear to the dictates of his own reason. He would rather question others and ponder on what the ancients have written than consult his own thoughts about what judgement he should make. From childhood he has taken for reason what rested only on the authority of his teachers; so now he puts forward his own authority as reason, and is anxious that others should submit to him in the way that he himself once submitted to others. But I shall have cause to be content, and shall regard myself as having more than adequately answered the objections which Epistemon put to you, if only you agree with what I shall say, and your own reason convinces you of it.
Epistemon I am not so pigheaded or so difficult to persuade and satisfy as you think. And although I had reason to lack confidence in Polyander, I am positively eager to submit our dispute to his arbitration. As soon as he comes down on your side, I promise to admit defeat. But he must take care not to let himself be deceived or to make the mistake for which he reproaches[8] others, i.e. to regard his esteem for you as a convincing reason for believing what you say.
Eudoxus If he relied on such a feeble basis for belief, he would surely be neglecting his own interests, and, I vouch, he will look after himself in this matter. But let us get back to our subject. I quite share your view, Epistemon, that we must know what doubt is, what thought is, what existence is, before being convinced of the truth of this inference, ‘I am doubting, therefore I exist’, or what amounts to the same thing, ‘I am thinking, therefore I exist’. But do not imagine that in order to know what these are, we have to rack our brains trying to find the ‘proximate genus’ and the ‘essential differentia’ which go to make up their true definition. We can leave that to someone who wants to be a professor or to debate in the Schools. But someone who wants to examine things for himself, and to base his judgements about them on his own conceptions, must surely have enough mental capacity to have adequate knowledge of what doubt, thought and existence are, whenever he attends to the question, without having to be taught the difference between them. Besides, there are, in my view, some things which are made more obscure by our attempts to define them: since they are very simple and clear, they are perceived and known just on their own, and there is no better way of knowing and perceiving them. Perhaps some of the most serious errors in the sciences are those committed by those who try to define what should only be conceived, and who cannot distinguish between what is clear and what is obscure, nor tell the difference between something which needs and merits a definition if it is to be known and something which is best known just on its own. But doubt, thought and existence can be regarded as belonging to the class of things which have this sort of clarity and which are known just on their own.
I would never have believed that there has ever existed anyone so dull that he had to be told what existence is before being able to conclude and assert that he exists. The same applies to doubt and thought. Furthermore, the only way we can learn such things is by ourselves: what convinces us of them is simply our own experience or awareness — that awareness or internal testimony which everyone experiences within himself when he ponders on such matters. Thus it would be pointless trying to define, for someone totally blind, what it is to be white: in order to know what that is, all that is needed is to have one’s eyes open and to see white. In the same way, in order to know what doubt and thought are, all one need do is to doubt or to think. That tells us all it is possible to know about them, and explains more about them than even the most precise definitions. So it is true that Polyander must have known these things before being able to draw the conclusions which he did. But, since we chose him as judge, let us ask him if he has ever been ignorant of what doubt or thought or existence is.
Polyander I am quite delighted, I must admit, to hear you arguing about something which you could learn only from me. I am pleased to see that on this occasion at any rate you must acknowledge me as your teacher and regard yourselves as my pupils. So to put both of you out of your misery, I shall solve your problem at a stroke (it is totally unexpected events which we say happen ‘at a stroke’). I can say for sure that I have never doubted what doubt is, though I only began to recognize it, or rather to give my attention to it, when Epistemon tried to cast doubt on it. As soon as you showed me what little certainty we can have in the existence of things which we can know only by means of the senses, I began to doubt them. This was enough to bring my doubt home to me and to make me certain of it. Thus I can state that as soon as I began to doubt, I began to have knowledge which was certain. But my doubt and my certainty did not relate to the same objects: my doubt applied only to things which existed outside me, whereas my certainty related to myself and my doubting. So Eudoxus was right when he said that there are things we cannot know about unless we see them. In order, then, to know what doubt and thought are, all we need do is to doubt and to think. The same applies to existence: to know what that is, all we need do is to understand the meaning of the word, for that tells us at once what the thing is which the word stands for, in so far as we can know it. There is no need here for a definition, which would confuse rather than clarify the issue.
Epistemon Since Polyander is satisfied, I too shall agree, and I shall not press the argument any further. But, after two hours of discussion, I cannot see that he has made much progress. All Polyander has learnt with the aid of this marvellous method which you are making such a song about is the fact that he is doubting, that he is thinking, and that he is a thinking thing. Marvellous indeed! So many words for such a meagre result. Four words could have done the trick, and we should all have agreed about it. As for myself, if I were required to spend so much time and engage in such a long discussion in order to learn such an insignificant fact, I would be very reluctant to make the effort. Our teachers have so much more to tell us, and they do so with much more assurance. Nothing holds them back; they deal with everything themselves, and decide each point. Nothing deflects them from their purpose; nothing takes them by surprise. When they feel themselves pressed too hard on some point, an equivocation or a distinction gets them out of their difficulties. You can be sure that their method will always be preferred to yours, which casts doubt on everything, and has such a fear of tripping up that it is constantly dithering and making no headway.
Eudoxus It was never my intention to prescribe to anyone the method which he should follow in his search for truth, but simply to describe the method which I used myself: if it should be thought to be defective, it would be rejected; if good and useful, others would use it too. I left it up to each individual to use it or reject it entirely as he saw fit. If someone should now say that it has not got me very far, this is a matter for experience to determine. Provided you continue to give me your attention, I am sure you will admit that we cannot be too careful in establishing our first principles, and that once these are established, the consequences will be able to be deduced more easily, and will take us further, than we dared hope was possible. All the mistakes made in the sciences happen, in my view, simply because at the beginning we make judgements too hastily, and accept as our first principles matters which are obscure and of which we do not have a clear and distinct notion. That this is true is shown by the slight progress we have made in the sciences whose first principles are certain and known by everyone. By contrast, in the case of sciences, whose principles are obscure and uncertain, those who are prepared to state their views honestly must admit that, for all the time they have spent reading many a vast tome; they have ended up realizing that they know nothing and have learnt nothing. So, my dear Epistemon, you should not be surprised that I wish to lead Polyander along a more certain path than the one I was led along myself, and that I am so careful and precise as to take nothing to be true if I am not as sure of it as I am of the certain fact that I exist, and am thinking, and am a thinking thing.
Epistemon You seem to me to be like an acrobat who always lands on his feet, so constantly do you go back to your ‘first principle’. But if you go on in this way, your progress will be slow and limited. How are we always to find truths such that we can he as firmly convinced of them as we are of our own existence?
Eudoxus That is not as difficult as you think. For all truths follow logically from one another, and are mutually interconnected. The whole secret is to begin with the first and simplest truths, and then to proceed gradually and as it were step by step to the most remote and most complex truths. Now can anyone doubt that what I have laid down as the first principle is the first of all the facts we can get to know if we proceed more methodically? It is certain that we cannot doubt this, even if we doubt the truth of everything in the universe. Since, then, we are sure that we have made the right beginning, we must see to it that we do not go wrong from now on. We must take great care to admit as true nothing which is open to even the slightest doubt. With this in view, I say we should let Polyander speak on his own. The only master he follows is common sense, and his reason has not been marred by any false preconceptions. So it is hardly likely that he will be deceived; if he were, he would soon realize it, and would have no trouble getting back onto the road. So let us hear what he has to say; let him tell us about the things which, so he told us, he saw to be contained in our[9] first principle.
Polyander So many things are contained in the idea of a thinking thing that it would take whole days to unfold them. We shall be dealing for the moment only with the most important things, and with those which help to make the notion of a thinking thing more distinct, and which will help us to avoid confusing it with notions which have nothing to do with it. By a ‘thinking thing’ I mean…[10]
[1] Diogenes of Sinope (fourth cent. B.C.), one of the founders of the Cynic school of philosophy, was celebrated in antiquity for residing in a large earthenware tub.
[2] Socrates attributed his reputation as the wisest man in Athens to the fact that he alone recognized that he knew nothing. Pyrrhonism was a strong version of scepticism which advocated complete suspension of judgement (named after Pyrrhon of Elis, born c. 365 B.C.).
[3] Cf. above p. 101.
[4] Here the French manuscript ends; what follows is translated from the Latin of the Amsterdam edition (1701).
[5] Porphyry, one of the founders of Neoplatonism (born c. 237 A.D.), proposed a ‘family tree’ of genera and species under which things may be classified. Thus the genus, substance (the ‘trunk’ of the tree), branches into the two species, corporeal and incorporeal, each of which divides into a further pair, etc. — for example, corporeal into living and non-living, living into sentient and non-sentient, etc. Cf. above p. 344.
[6] AT suggest that ‘you’ (tut) is a misprint for ‘me’ (mei).
[7] Two of the problems of Greek mathematics — both unsolvable: the former, to construct a circle with the same area as a given square; the latter, to construct a cube which is twice the volume of a given cube.
[8] Lat. exprobat (‘he reproaches’) may be a misprint for exprobras (‘you reproach’).
[9] The Amsterdam edition (1701) has ‘your’ (vestro), but the sense requires ‘our’ (nostro). One might, alternatively, give this sentence to Epistemon.
[10] The Amsterdam edition inserts here the sentence, ‘The rest is missing.’