A. The project of pure inquiry.
This expression, taken from Bernard Williams' book Descartes: The Project of Pure Inquiry, admirably captures Descartes' general aim. Descartes proposes to examine the grounds we have for the various things we believe in complete independence from practical considerations that make it necessary for us to believe, or at least to tentatively accept, many propositions in order to get along in the world. Descartes recognizes these practical necessities, of course, but nevertheless finds it worthwhile to engage in a purely theoretical examination of the reasons we have for our beliefs.
Descartes' project involves starting from scratch. He wants to begin by presupposing nothing. The fact that he finds himself believing something is not automatically a reason for thinking it true; neither is the fact that other people have believed it, no matter how many people, how firm their belief, how long they have believed it, or how highly regarded they are. Descartes will begin by taking nothing for granted. It may be in the end that the conventional sources of wisdom will be vindicated, but it will not do to begin by assuming that they are reliable; only a compelling argument can show that. Descartes proposes to conduct this investigation into the warrant for our beliefs by doubting everything until it has been shown to be an acceptable belief.
Surely it must have struck most of us at one time or other that such a project would be extremely valuable. It is often forcibly brought home to us that we believe a good deal that is false, and when this happens we become vividly aware that our procedures for discriminating truths from falsehoods are not very reliable, and long for a more adequate procedure. The project of pure inquiry may be motivated by what Alasdair MacIntyre has called an "epistemological crisis."
Such a crisis involves a discovery which forces one to reinterpret a great deal of evidence whose explanation one had felt certain one understood. One might, for example, suppose on what seemed compelling evidence that a certain person was one's friend. Despite all one's evidence it might one day become perfectly clear that this person did not care about one at all. Suddenly everything the person did would be seen in a new light: actions that had seemed spontaneous would now be seen as calculated and scheming; actions that had seemed signs of affection would now seem deliberately deceptive expressions of pure self-interest; actions that had seemed generous or selfless would now seem greedy and grasping.
This sort of experience can be profoundly unsettling. One may naturally be led to the quite dismaying thought that if one could have been so mistaken about this acquaintance, one could well be mistaken about any of one's acquaintances. (One could also have the further worry that one could be mistaken about all of one's acquaintances, but this seems psychologically less likely--and for good reason, since the possibility of error about every case does not follow from the possibility of error about any case. Compare: anyone now alive could become the last person on earth, but it could not happen that everyone now alive became the last person on earth.) It may well seem at such a time that the only alternative to the discovery of a foolproof means of distinguishing true friends from false is this sort of damaging wholesale skepticism.
One consequence of Descartes' determination to begin from scratch was a refusal to accept any belief on authority, and thus an increased emphasis on the importance of the individual in working out his or her own beliefs. (In this respect Descartes' influence might be compared with that of Luther a century before.) This was during a period in which the influence of the Church in matters of belief was still very strong: Descartes' principal philosophical works, the Discourse on the Method and the Meditations, were published in 1637 and 1641, respectively; it was only a few years earlier, in 1633, that Galileo was condemned and sentenced to life imprisonment by the Inquisition for maintaining that the Earth moved. (Indeed Descartes' knowledge of Galileo's condemnation led him to be fearful of condemnation by the Church; he went so far as to suppress his first scientific work, to have been called Treatise on the Universe. And it should be noted that Descartes did not mean to be subversive; indeed, he hoped that his views would become official Catholic teaching, and wrote a textbook (the Principles, 1644) in hope of furthering this end.)B. Knowledge requires certainty.
The goal of Descartes' project is to acquire knowledge of the truth. He proposes to achieve this by doubting every proposition he has insufficient reason for believing, and adding a proposition to his store of beliefs only when he has demonstrated that there is ample reason to believe it. But, for Descartes, we do not have "ample reason" for believing anything unless it is completely certain. He writes, for example, that "reason already convinces me that I must withhold assent no less carefully from what is not plainly certain and indubitable than from what is obviously false" (First Meditation). Similarly, he notes in the Fourth Meditation that we fall into error when we make judgments about things we do not clearly and distinctly perceive. Since we can be certain of the truth of what we clearly and distinctly perceive, and since we should not pass judgment on anything we do not clearly and distinctly perceive, it seems that we should refrain from believing anything we cannot be certain of. [So what about scientific hypotheses which are merely probable? I dont think Descartes means to regard them as entirely illegitimate; rather, the idea must be that we should not regard them as knowledge, but merely as conjecture: we may accept them "for the sake of argument," to see what we can get out of them, but should not actually believe them. This may seem odd, but it is not so different from the recommendation of some contemporary philosophers of science, e.g. Karl Popper and Bas van Fraassen.]C. I am certain of the contents of my own mind.
Descartes thinks that there is at least one truth which is indubitable, which I cannot doubt: the truth that I exist. And I can know a good deal about my nature--in particular that I am conscious, which Descartes takes to mean that I am "a being that doubts, understands, asserts, denies, is willing, is unwilling; further, that has sense and imagination" (Second Meditation). The view that I can be certain about what is going on in my own mind has been usefully termed "epistemological transparency" (by Margaret Wilson).
(It is worth taking an inventory of Descartes' catalog of mental states. They seem to fall into three groups. There are theoretical mental states, which have to do with whether we take propositions to be true or false: doubting, asserting, denying. There are practical mental states, which have to do with whether we make propositions true or false (being willing or unwilling). And there are phenomenological mental states, which have to do with what we experience (sensation). We will later see something very similar to this threefold distinction given great importance in Kant, who attributes them to the mental faculties of Understanding, Reason, and Sensibility.)D. Uncertainty about the external world.
There is a great epistemological divide, for Descartes, between the facts about our own mental experience and the facts about the external world: we are quite immediately certain, Descartes believes, about the contents of our own minds, but all our beliefs about the external world are at least initially subject to doubt. Our information about the external world comes to us through our senses, which sometimes deceive us; but if our senses are sometimes mistaken, then they could be mistaken on any occasion, and so all beliefs which we arrive at by their means must be doubted. Thus Descartes opens a great gulf between the inner and outer worlds, a gulf which has haunted philosophy ever since.
Of course Descartes tries, later in the Meditations, to win back certainty about the external world via a "proof" of the existence of God together with the view that God is not a deceiver. The crucial fact remains, however, that there is a prima facie difficulty about our knowledge of the external world. Descartes thinks that this is very different from our situation with respect to our own minds.E. The mind-body distinction.
Arguably, our contemporary distinction between the mind and the body is one which we owe to Descartes. Descartes groups together into one category phenomena which were not previously thought of as of a piece. To see this, we need two distinctions. First, there is the distinction between intentional and nonintentional phenomena. Intentional phenomena are things which represent or are about other things. If I believe that grass is green, my belief is about grass and represents grass as being a particular color. If I want the Dolphins to win the Super Bowl, my desire is about the Dolphins and represents them as winning the Super Bowl. But rocks are not about anything and do not represent anything, and neither do pains. So rocks and pains are not intentional, while beliefs and desires are. A second distinction is that between phenomenal and non-phenomenal things. A phenomenal event or thing is a feeling or sensation--like pain, or the sensation of blue, or a ringing in your ears. Putting these two distinctions together, we get four possible combinations:
|"occurrent" beliefs, mental images||"dispositional" beliefs, desires, etc.|
|"raw feels" (e.g. pain, babies experiences)||the "merely physical" (rocks, trees, etc.)|
(I have adapted this chart from Richard Rorty, Philosophy and the Mirror of Nature, p. 24.)
Some scholars believe that Descartes essentially invented the modern conception of the mental by grouping intentional and phenomenal occurrences together into a single category.
So far I have discussed the point at which Descartes draws the line between mental and non-mental phenomena. The suggestion has been that Descartes' collecting the intentional and the phenomenal into a single category is an innovation. But there is a further important point to note about Descartes' mind-body distinction. Descartes locates mental and non-mental phenomena in separate substances. He argues that nonmental phenomena are characteristics of physical substance, while mental phenomena are characteristics of an utterly different sort of stuff, mental or spiritual substance.
There are two trains of thought which can be seen as evolving out of Descartes' views. His rationalist successors, Spinoza and Leibniz, were not terribly troubled by Descartes' confidence that what we clearly and distinctly perceive must be true, or by his proofs of Gods existence, but they were worried about his view that minds and bodies are composed of utterly different kinds of substance which nevertheless interact.
Descartes' empiricist successors are increasingly worried by his views about substance, though for different reasons than the rationalists. But they are most moved by his invention or discovery of a great chasm between our internal mental world and the external world about which we would like to know more. The empiricists find Descartes' problems and many of his methods compelling but find his rescue of the external world via a proof of God's existence utterly unconvincing. Someone who accepts Descartes' project and assumptions but rejects the proof of God is likely to be led in one of two directions. One might retain a belief in the existence of an external world separate and distinct from our mental worlds, but become skeptical about the possibility of knowledge of this world; or one might insist that we have knowledge of the "external" world, retaining this belief by denying that the external world is really separate or distinct from the mental world. If the "external" world is just a kind of mental construct; if spiritual substance is the only sort of substance and material substance is just a philosophical mistake, then our knowledge of the world may be just as direct and unproblematic as our knowledge of our own minds. The former possibility, skepticism, was to be brilliantly embraced by David Hume; the latter possibility, idealism, may be seen at its starkest and most dramatic in the philosophy of George Berkeley.