Philosophy Sample Paper - Stanford University



Philosophy Sample Paper

Cartesian Doubt

Allen Wood

In the first of Descartes’ Meditations, he sets out to give reasons “for doubt about all things” (12).[i] Descartes gives us two reasons for starting philosophical inquiry with this universal doubt: doubting all things (i) frees us from “all our preconceived opinions” and (ii) “provides the easiest route by which the mind may be led away from the senses” (12). At the end of this paper I will have a little to say about the overall philosophical strategy of which these reasons are a part. But my main concern here will be Descartes’ attempt to give “powerful and well thought-out reasons” for doubting everything he previously believed (21).

Descartes’ reasons for doubting everything are presented in three stages. Each stage of his argument undermines a successively larger class of beliefs, by undermining the “basic principles” that support that class of beliefs (18). The first stage uses what we may call the sense deception argument, which attacks the principle that we should believe whatever our senses incline us to believe. The sense deception argument is grounded on the fact that beliefs based on the senses (which we may call “sense beliefs”) have sometimes been found to have been mistaken. (From a distance, a square tower looks round; from across the room, a tiny speck of dirt on the wall looks like an insect.) It also uses the principle that it is prudent never wholly to trust things that have once deceived us. Therefore, it is reasonable to doubt (at least slightly) all our sense beliefs (18).

As Descartes immediately observes, the sense deception argument is capable of rendering doubtful only some of our sense beliefs. The ways I have been deceived by the senses in the past do give me grounds for doubting sense beliefs about objects that are “very small or in the distance” (18), but they do not give me any reason to doubt sense beliefs about large objects that are quite close to me. The sense deception argument, for instance, gives me no good reason for doubting that I am right now wearing clothes or looking at a piece of paper with words printed on it. Only someone who is insane, he says, could have mistaken sense beliefs about things like that (19). If Descartes wants to show that sense beliefs generally are doubtful, he will have to use a different argument from the sense deception argument.

That is what he does, by presenting the dreaming argument. Descartes notes that sometimes he dreams and while he dreams he often has false sense beliefs even about objects that are apparently large and close to him (19). Further, Descartes claims that “there are never any sure signs by means of which being awake can be distinguished from being asleep” (19). That is, there is no feature belonging directly to individual sensations or sense-beliefs that enables one to know for certain whether a given one is a waking or dreaming sensation or sense-belief. So at any time there is at least a slight possibility that I am asleep and dreaming, and that all my sense-beliefs are therefore false. Therefore, there is always at least a slight possibility that I am dreaming, and hence all my sense-beliefs, not merely those about small or distant objects, are to some extent doubtful.

The dreaming argument does give us reasons for doubting all our sense beliefs. But it does not give us reasons for doubting many of our other beliefs, which Descartes describes as beliefs about “general kinds of things”, such as colors (20).[ii] Perhaps he has in mind my belief that red and green are colors and that red is a different color from green. Though I may become acquainted with red and green through the senses, I do not rely on my present sense perceptions to tell me that red is a different color from green, and the judgment that red is different from green is equally certain whether I make it while awake or while dreaming about red and green. Many other beliefs, such as those about mathematical objects, are immune to the dreaming argument for similar reasons (20). If I judge that a square has four sides, or that two plus three equals five, this is equally certain whether I am awake or dreaming. And if either of Descartes’ arguments for God’s existence are sound (36-51, 65-68), then they are equally sound whether I think of them while awake o dreaming.

In the first of his Meditations, however, Descartes wants to argue for universal doubt. He does so by means of a third argument, which is usually identified with the hypothesis of a deceiving God or a “malicious demon” who has the power and the will to deceive me even abut those matters of which I am most certain (22). But a close look at Descartes’ text reveals that the real heart of the argument is that all my beliefs are doubtful because I cannot be absolutely certain that I am not making a mistake even in matters where I am most confident. Just as I sometimes think that “others go astray in cases where they think they have the most perfect knowledge,” so I cannot be sure that I do not go wrong too whenever I do something such as add two and three or count the sides of a square (21).[iii] The hypothesis of the malicious demon or deceiving God is only one way of dramatizing our fallibility, and of course it will also play a role in Descartes’ escape from universal doubt later in the Meditations.

Thus I propose to call Descartes’ third and final argument for doubt the fallibility argument. The fallibility argument may be represented as follows:

1. For any subject matter M, if it is possible that I have made a mistake about M, then I have a good reason for doubting my beliefs about M.

2. I cannot be perfectly certain that I have not made a mistake about any matter, no matter how simple it might be.

3. Therefore, for any matter M, it is possible that I am mistaken about M.

4. Therefore, I have a good reason for doubting all my belief about any and every matter.

Despite its simplicity, the fallibility argument is powerful and convincing. (3) follows from (2), and (4) follows from (1) and (3); hence the argument is valid. But both premises (1) and (2) are true, as far as we can tell. (1) is a correct epistemological principle, and we should accept (2) until we have some way of ruling out at least for some matters that we might be mistaken about them. Therefore, the argument is sound, and its conclusion must be true.[iv]

Let us consider two objections that might be brought against the fallibility argument. The first says that the argument is defective because it assumes as certain that our faculties are defective, whereas the truth is that this is much less certain than that red is different from green or two plus three equals five. But the objection is mistaken, because the fallibility argument does not require that we be certain that our faculties are defective. It is sufficient if we do not know for certain that we are not making an error in any given matter we may consider. Even a very doubtful supposition is enough to cast some slight doubt on beliefs that would be false if the supposition were true.

The second objection says that the fallibility argument is self-defeating because if our faculties are so defective that we are mistaken even in adding two and three, then it follows equally that we may be mistaken in inferring (4) from (1), (2) and (3), and so the fallibility argument itself might equally be mistaken. But this second objection is based on the same error as the first objection. For I need not be reasoning correctly in order to use my reasoning to cast doubt on some matter. Suppose, for instance, that I add 235 and 347 quickly in my head and get the answer 572; to check my addition, you quickly add the same figures in your head and get 582. At this point you would be quite justified in doubting my answer, even though you are far from certain that your hasty calculation is correct. Probably both answers are uncertain for you at least until you do more careful calculations. Likewise, Descartes may use the fallibility argument without assuming the infallibility of his reasoning in it.

Both objections make the same mistake by supposing that if we doubt something for a reason, we have to be certain of the reason. But that is false. We may doubt for a good reason even while also doubting the very reason why we doubt.

The fallibility argument is therefore successful. It does show that all our beliefs are to some extent doubtful. Of course, as Descartes notes, the degree of this doubt is not great. It does not justify any hesitation in making use of our previous beliefs for practical purposes, at least until they have been show to be false by the science Descartes intends to build. Such beliefs, Descartes says, are “highly probable opinions” which it is “much more reasonable to believe than deny” (22). I treat them as doubtful because “the task now at hand does not involve action but merely the acquisition of knowledge” (22).

The importance of Cartesian Doubt lies not in its magnitude but in its methodological function. Descartes aim in the Meditations is to establish a new foundation for the sciences, and for a new scientific view of the world that is in many ways at odds with both ordinary common sense and with what our senses seem to tell us about the world (as well as with scholastic philosophy, which was much more empirical than modern science is). Descartes’ strategy is this: First (a) call all our beliefs into doubt. Next (b) try to discover a way of establishing a few beliefs that are so “metaphysically” certain (36) that no doubt about them is even thinkable. Then finally (c) try to erect the new science on the firm foundation of those few metaphysically certain beliefs. It has not been my purpose in this paper to decide whether Descartes is successful in stages (b) and (c) of his project. But I have shown that until he finds something that is metaphysically certain, Descartes’ fallibility argument does successfully achieve the goals of stage (a). It shows that at least for the time being, all our beliefs are metaphysically doubtful.

Notes

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[i] Descartes’ Meditations on First Philosophy will be cited according to the pagination, given marginally in all recent English translations, from the standard edition of Descartes’ works: Charles Adam and Paul Tannery (eds.), Oeurvres de Descartes (Paris: Cerf, 1897-1913). The Meditations is in Volume 7 of this edition. Quotations will be from John Cottingham (ed.) Descartes, Meditations on First Philosophy (Cambridge: Cambridge University Press, 1996).

[ii] From what Descartes says later (29-30, 44), it seems doubtful that he actually regards colors as genuine examples of “general things”, since he seems to treat them as illusions of sense, that do not really belong to the nature of bodies. He appears to think that it is only things like quantity, shape and metaphysical perfection, not merely sensible qualities, such as color, sound, heat and cold, that constitute genuine “general kinds of things”. But I will ignore this problem here, as Descartes apparently does.

[iii] We can see that the crucial point in the argument is our fallibility and not the existence or non-existence of an “evil genius”, if we look at the parallel passage in Part Four of Descartes’ Discourse on Method. There his argument for universal doubt does not even mention the deceiving God or evil genius, but consists in saying only that he is “prone to error” in his reasonings (Descartes, Oeuvres, ed. Adam and Tannery, cited in note 1, Volume 6, p. 32).

[iv] Philosophers call an argument “valid” when its conclusion follows from its premises, whether or not the premises are true. Thus the following argument is valid: “If 2+3=6, then you are a fish; 2+3 = 6; therefore, you are a fish.” An argument is said to be “sound” when it is valid and the premises are true. The conclusion of a sound argument, unlike that of a merely valid argument, has to be true.

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