As soon as he had completed the Meditations, Descartes began to circulate them among his friends, asking for comments and criticisms. He also sent the manuscript to Friar Marin Mersenne (1588–1648), his friend and principal correspondent, asking him to obtain further criticisms. He wrote to Mersenne in a letter of 28 January 1641: ‘I shall be glad if people make me as many objections as possible – and the strongest ones they can find. For I hope that in consequence the truth will stand out all the better.’ The resulting six sets of Objections (the first set collected by Descartes himself, the remainder by Mersenne) were published in Latin, together with Descartes' Replies, in the same volume as the first (1641) edition of the Meditations. The second edition of the Meditations (1642) contained in addition the Seventh Set of Objections together with Descartes' Replies, and also the Letter to Dinet (all in Latin). The terms ‘Objections’ and ‘Replies’ were suggested by Descartes himself, who asked that his own comments should be called ‘Replies’ rather than ‘Solutions’ in order to leave the reader to judge whether his replies contained solutions to the difficulties offered (letter to Mersenne, 18 March 1641).

The volume containing the French translation of the Meditations (by de Luynes), which appeared in 1647, also contained a French version of the first six sets of Objections and Replies by Descartes' disciple Claude Clerselier (1614–84).

During these past few days I have accustomed myself to leading my mind away from the senses; and I have taken careful note of the fact that there is very little about corporeal things that is truly perceived, whereas much more is known about the human mind, and still more about God. The result is that I now have no difficulty in turning my mind away from imaginable things and towards things which are objects of the intellect alone and are totally separate from matter. And indeed the idea I have of the human mind, in so far as it is a thinking thing, which is not extended in length, breadth or height and has no other bodily characteristics, is much more distinct than the idea of any corporeal thing. And when I consider the fact that I have doubts, or that I am a thing that is incomplete and dependent, then there arises in me a clear and distinct idea of a being who is independent and complete, that is, an idea of God. And from the mere fact that there is such an idea within me, or that I who possess this idea exist, I clearly infer that God also exists, and that every single moment of my entire existence depends on him. So clear is this conclusion that I am confident that the human intellect cannot know anything that is more evident or more certain.

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 book-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.

1. It is true that no one can be certain that he is thinking or that he exists unless he knows what thought is and what existence is. But this does not require reflective knowledge, or the kind of knowledge that is acquired by means of demonstrations; still less does it require knowledge of reflective knowledge, i.e. knowing that we know, and knowing that we know that we know, and so on ad infinitum. This kind of knowledge cannot possibly be obtained about anything. It is quite sufficient that we should know it by that internal awareness which always precedes reflective knowledge. This inner awareness of one's thought and existence is so innate in all men that, although we may pretend that we do not have it if we are overwhelmed by preconceived opinions and pay more attention to words than to their meanings, we cannot in fact fail to have it. Thus when anyone notices that he is thinking and that it follows from this that he exists, even though he may never before have asked what thought is or what existence is, he still cannot fail to have sufficient knowledge of them both to satisfy himself in this regard.

2. When someone notices that he is thinking, then, given that he understands what motion is, it is quite impossible that he should believe that he is mistaken and is ‘not thinking but merely in motion’.

I could not possibly wish for a more perceptive or more courteous critic of my book than the gentleman whose comments you have sent me. He has dealt with me so considerately that I can easily perceive his goodwill towards myself and the cause that I defend. At the same time, where he has attacked me he has looked into the issues so deeply, and examined all the related topics so carefully, that I am sure that there are no outstanding difficulties elsewhere that have escaped his watchful attention. What is more, where he thinks my views are not acceptable, he has pressed his criticisms so acutely that I am not afraid of anyone's supposing that he has kept back any objections for the sake of the cause. In view of this, I am not so much disturbed by his criticisms as happy that he has not found more to attack.

REPLY TO PART ONE, DEALING WITH THE NATURE OF THE HUMAN MIND

I shall not waste time here by thanking my distinguished critic for bringing in the authority of St Augustine to support me, and for setting out my arguments so vigorously that he seems to fear that their strength may not be sufficiently apparent to anyone else.

So serious are the doubts into which I have been thrown as a result of yesterday's meditation that I can neither put them out of my mind nor see any way of resolving them. It feels as if I have fallen unexpectedly into a deep whirlpool which tumbles me around so that I can neither stand on the bottom nor swim up to the top. Nevertheless I will make an effort and once more attempt the same path which I started on yesterday. Anything which admits of the slightest doubt I will set aside just as if I had found it to be wholly false; and I will proceed in this way until I recognize something certain, or, if nothing else, until I at least recognize for certain that there is no certainty. Archimedes used to demand just one firm and immovable point in order to shift the entire earth; so I too can hope for great things if I manage to find just one thing, however slight, that is certain and unshakeable.

I will suppose then, that everything I see is spurious. I will believe that my memory tells me lies, and that none of the things that it reports ever happened. I have no senses. Body, shape, extension, movement and place are chimeras. So what remains true? Perhaps just the one fact that nothing is certain.

Yet apart from everything I have just listed, how do I know that there is not something else which does not allow even the slightest occasion for doubt?

Some years ago I was struck by the large number of falsehoods that I had accepted as true in my childhood, and by the highly doubtful nature of the whole edifice that I had subsequently based on them. I realized that it was necessary, once in the course of my life, to demolish everything completely and start again right from the foundations if I wanted to establish anything at all in the sciences that was stable and likely to last. But the task looked an enormous one, and I began to wait until I should reach a mature enough age to ensure that no subsequent time of life would be more suitable for tackling such inquiries. This led me to put the project off for so long that I would now be to blame if by pondering over it any further I wasted the time still left for carrying it out. So today I have expressly rid my mind of all worries and arranged for myself a clear stretch of free time. I am here quite alone, and at last I will devote myself sincerely and without reservation to the general demolition of my opinions.

But to accomplish this, it will not be necessary for me to show that all my opinions are false, which is something I could perhaps never manage.

On the First Meditation (‘What can be called into doubt’)

FIRST OBJECTION

From what is said in this Meditation it is clear enough that there is no criterion enabling us to distinguish our dreams from the waking state and from veridical sensations. And hence the images we have when we are awake and having sensations are not accidents that inhere in external objects, and are no proof that any such external object exists at all. So if we follow our senses, without exercising our reason in any way, we shall be justified in doubting whether anything exists. I acknowledge the correctness of this Meditation. But since Plato and other ancient philosophers discussed this uncertainty in the objects of the senses, and since the difficulty of distinguishing the waking state from dreams is commonly pointed out, I am sorry that the author, who is so outstanding in the field of original speculations, should be publishing this ancient material.

Reply

The arguments for doubting, which the philosopher here accepts as valid, are ones that I was presenting as merely plausible. I was not trying to sell them as novelties, but had a threefold aim in mind when I used them. Partly I wanted to prepare my readers' minds for the study of the things which are related to the intellect, and help them to distinguish these things from corporeal things; and such arguments seem to be wholly necessary for this purpose.

After a very careful reading of your Meditations and of your replies to the objections so far raised, we find there are still some difficulties remaining, which it is only fair to ask you to remove.

The first point is that from the fact that we are thinking it does not seem to be entirely certain that we exist. For in order to be certain that you are thinking you must know what thought or thinking is, and what your existence is; but since you do not yet know what these things are, how can you know that you are thinking or that you exist? Thus neither when you say ‘I am thinking’ nor when you add ‘therefore, I exist’ do you really know what you are saying. Indeed, you do not even know that you are saying or thinking anything, since this seems to require that you should know that you know what you are saying; and this in turn requires that you be aware of knowing that you know what you are saying, and so on ad infinitum. Hence it is clear that you cannot know whether you exist or even whether you are thinking.

To come to the second difficulty, when you say you are thinking and that you exist, someone might maintain that you are mistaken, and are not thinking but are merely in motion, and that you are nothing else but corporeal motion.

Letter to a distinguished gentleman

Sir,

Though you have done me a kindness, you certainly want your reward. Indeed, you are exacting a heavy price for the great favour you have done me, in that you have allowed me to see this brilliant work only on condition that I should make public my opinion of it. This is certainly a hard condition, which only my eagerness to see this superb piece of work has driven me to accept; and I would gladly try to get out of it if, instead of the traditional Praetor's dispensation applying to contracts entered into ‘through force or fear’, I could claim a new excusing condition applying to those ‘made under the influence of pleasure’.

What exactly do you want? You can hardly be after my opinion of the author, since you already know how highly I rate his outstanding intelligence and exceptional learning. Moreover, you know of all the tedious commitments that keep me busy, and if you have an unsuitably high opinion of my powers, that certainly does not make me any less aware of my own inadequacy. Yet the work you are giving me to scrutinize requires both an uncommon intellect and, above all, a calm mind, which can be free from the hurly-burly of all external things and have the leisure to consider itself – something which, as you are well aware, can happen only if the mind meditates attentively and keeps its gaze fixed upon itself.

The Search for Truth by means of the Natural Light (La Recherche de La Vérité par la lumière naturelle) is an incomplete work which was not published during Descartes' lifetime. In the inventory of Descartes' papers, made after his death in Stockholm, the work is listed as ‘thirteen pages of a Dialogue with the title “The Search for Truth by means of the Natural Light”’. The work first appeared, in a Latin translation, in the collection of Descartes' posthumous works (Opuscula posthuma) edited by P. and J. Blaeu and published at Amsterdam in 1701.

The original French manuscript has been lost. Leibniz obtained a copy made by Tschirnhaus in 1676, and a part of this copy – roughly the first half of the published Latin translation – was discovered among Leibniz's papers in the Royal Public Library at Hanover. Adam and Tannery's edition comprises this French text, completed by the Latin translation of the Amsterdam edition.

The date of composition of the dialogue is a matter of conjecture. In his biography of Descartes, Baillet takes it to date from the last years of Descartes' life. Some scholars have suggested that it dates from Descartes' earlier years. And others have put forward the hypothesis that Descartes wrote it during the summer of 1641, while he was living in the castle of Endegeest and his thoughts were occupied with the central arguments of the Meditations and the objections of his scholastic critics, both of which find expression, though in a somewhat crude form, in the dialogue.

I recently wrote to the Reverend Father Mersenne about the essay which I had heard that Father Bourdin had written against me, and I indicated that I was very keen for him to publish it or at least send it to me so that I could have it published along with the remaining sets of objections which others had sent me. But when I asked him to get permission for this either from Father Bourdin, or indeed from Your Reverence, since I thought this the fairest course, he replied that he had already passed my letter on to you, and that you had not only been pleased with it but had also given him every indication of your singular concern, warmth and good-will towards me. And immediately afterwards I saw the proof of this myself, when the essay in question was sent to me. This leads me to express my utmost thanks to you, and also encourages me to tell you quite openly what I think of the essay, and to ask your advice about my projected studies.

When I held Father Bourdin's essay in my hands for the first time I was as happy as if I was clutching some great treasure.

The aim of this two-volume edition is to provide a completely new translation of the philosophical writings of Descartes, based on the original Latin and French texts. Although many of Descartes' philosophical works are now available in English either individually or in various selections, the only tolerably comprehensive edition remains that of Haldane and Ross, which first appeared in 1911. But although it has come to be regarded as the standard English edition, HR omits many works which are crucial for a full understanding of Descartes' philosophy. The present work, by contrast, aims to be as comprehensive as possible. Considerations of space have prevented us from being as inclusive as some, no doubt, would have wished; we have not, for example, included any of Descartes' letters, partly because an excellent selection is already available in English. But as well as including all the works to be found in Haldane and Ross, viz. the Discourse on the Method, Meditations, Objections and Replies, Rules for the Direction of the Mind, The Search for Truth, Comments on a Certain Broadsheet, The Passions of the Soul and selections from the Principles of Philosophy, we have also provided extracts from Descartes' Early Writings, from The World, Treatise on Man, Optics and Description of the Human Body; our selection from the Principles, moreover, includes many articles not translated in Haldane and Ross.

Sir,

Mersenne did me a great favour in allowing me to see your splendid book, the Meditations on First Philosophy. I am most impressed by your excellent arguments, your intellectual acumen and your brilliant style. And I am happy to congratulate you on the highly intelligent and successful way in which you have attempted to extend the boundaries of the sciences and explain matters which have remained highly obscure in all previous ages. Mersenne asked me, as a friend of his, to write to you if I had any unresolved doubts about your book, but it has been hard for me to comply with his request. I foresaw that I should simply be displaying my lack of intelligence if I did not accept your arguments, or rather my rashness if. I ventured to utter a word of opposition which would make me seem to be attacking you. Nonetheless, I have yielded to my friend, thinking that you would be sure to accept and approve of a plan that is more his than mine; and I am sure that your good nature will make you see that my intention was simply to uncover the reasons which gave rise to my doubts.

Descartes' most celebrated philosophical work was written in Latin during the period 1638–40, when the philosopher was living, for the most part, at Santpoort. This ‘corner of north Holland’, he wrote to Mersenne on 17 May 1638, was much more suitable for his work than the ‘air of Paris’ with its ‘vast number of inevitable distractions’. The work was completed by April 1640, and was first published in Paris in 1641 by Michel Soly under the title Meditationes de Prima Philosophiae (Meditations on First Philosophy); the subtitle adds ‘in which are demonstrated the existence of God and the immortality of the soul’. In earlier correspondence Descartes had referred to his work as the Metaphysics, but he eventually decided that ‘the most suitable title is Meditations on First Philosophy, because the discussion is not confined to God and the soul but treats in general of all the first things to be discovered by philosophizing’ (letter to Mersenne, 11 November 1640).

Descartes was not entirely satisfied with Soly as a publisher, and he arranged for a second edition of the Meditations to be brought out in Holland, by the house of Elzevir of Amsterdam. This second edition appeared in 1642, with a new and more appropriate subtitle, viz. ‘in which are demonstrated the existence of God and the distinction between the human soul and the body’.