Descartes and Dream Skepticism Revisited

Descartes and Dream Skepticism Revisited ROBERT HANNA 1. HERE tS A PUZZLZabout Descartes's Meditations. In the first Meditation Descartes is able to infect himself, as it were, with a profound skeptical difficulty about perceptual knowledge: what he calls "the principal reason for doubt, namely my inability to distinguish between being asleep and being awake.", But then in the sixth Meditation Descartes is prepared to solve and dismiss this very same difficulty in a mere paragraph; here we are told that "the exaggerated doubts of the last few days should be dismissed as laughable" (CSM: I I, 61; AT: VII, 89). Was the skeptical worry a mere ma/ad/e imaginaire? Few philosophers have been prepared to laugh along with Descartes. It has in fact become a philosophical commonplace that Descartes's homespun cure for his self-inflicted ailment, his own argument against dream skepticism , fails miserably. Hobbes, for instance, in the Third Set of Objections to the Meditationa, supplies with ease what has generally been regarded as a knockdown counterexample to Descartes's antiskeptical argument (CSM: 1I, 137; AT: VlI, 195-96). Descartes's apparent failure to answer his own skeptical problem naturally leaves post-Cartesian philosophers with the old, old difficulty first mentioned in the Theaetetm: "You see, then, that there is plenty of room for doubt, when we even doubt whether we are asleep or awake."" Rent De~."-,rtes,Meditations on First PhilosoplU, in The PhilosophicalWriling~ of Descartes, 3 vols., trans. J. Cottngham, R. Stoothoff, and D. Murdoch (Cambridge : Cambridge University Press, 1984--91), vol. II, p. 6t; OeuvresdeDescartes,ed. C. Adam and P. Tannery (Paris: L. C, erf, 19o4), vol.VII, p. 89. All further references to Descartes's philosophical writings within the text of this essaywillgive volume and page numbers from these twoeditions, signified bythe abbreviations 'CSM' and 'AT' respectively. ' See Plato's Thraetetm, 158c-d. Plato's use of dream skepticism in the Theaetetusinvolves interesting similarities to, and differences from, Descartes's use of it in the first Meditation. For Descartes, the dream skeptic is attempting to cast doubt on the commonsensical epistemological principle that at least sometimes, and perhaps most of the time, the senses can give us secure 378 JOURNAL OF THE HISTORY OF PHILOSOPHY 30:3 JULY 199~ That is: If I cannot tell the difference between waking and dreaming with certainty, then could not my apparently most secure or evident perceptual judgments turn out to be false? To be sure, untold numbers of philosophers--including Kant and G. E. Moore most famouslys--have taken a crack at solving the dream-skeptical problem. Yet it is by no means an exaggeration to say that these antiskeptics have had at best an indifferent success: philosophical consensus certainly suggests that the standard arguments against dream skepticism4 are no more successful than Descartes's own. To modify Kant's famous epigram about external-world skepticism,s the continuing failure to provide an adequate argument against dream skepticism constitutes a philosophical scandal. In my opinion, this lack of success stems at least in part from a failure to understand and to learn properly from Descartes's own argument strategy. Despite its air of flippancy, the single paragraph in which Descartes directly attacks dream skepticism involves a rather sophisticated argument--an argument far more effective and plausible than is usually recognized by interpreters and critics of the Meditations. Consequently, this argument calls out for more serious philosophical scrutiny. In what follows in this paper, I want to take a close look at Descartes's actual method of attack on dream skepticism. We shall discover that he is not in fact even trying to prove what most of his critics accuse him of failing to prove; nor is he trying to prove it in the way most of his interpreters have supposed. Descartes's antiskeptical strategy in the last paragraph of the sixth knowledge via perceptual judgments (CSM: II, :a; AT: 18). So Descartes is attacking the epistemological credentials of perceptual judgment, and by implication, the epistemological framework of common sense. (Later in the Meditations, of course, these credentials and this framework are partially reinstated, although with special qualifications.) Plato on the other hand offers the dream...