MEDITATIONS ON THE DREAM ARGUMENT

Yakir LEVIN Ben-Gurion University of the Negev, Beer-Sheva

To the memory ofYael Cohen, a teacher and friend. "Let us show our feeling for our lost friends not by lamentation but by meditation." Epicurus.

Descartes' Dream Argument! starts with the claim:

(1) We cannot know that those of our experiences in which we seem to perceive an e~temal world, or exteriences as I will call them, are not in fact dreams.

Its second premise is:

(2) For exteriences to yield knowledge about the world we must know that they are not dreams.

These two premises immediately entail:

(3) We cannot know anything about the world through exterien• ces-

1. Rene Descartes, Meditations on the First Philosophy, trans. 1. Cottingham (Cambridge: Cambridge University Press, 1986), First Meditation. According to the most common line of interpretation the Dream Argument identifies knowl• edge with absolute certainty; cf., Margaret Dauler Wilson, Descartes, (London: Routledge and Kegan Paul, 1978), pp. 11-31. On another line the argument as• sumes a much broader notion of knowledge (see the references to Stroud and Steiner below). The first line is perhaps more faithful to Descartes' intentions, while the second is more relevant to contemporary concerns. In this paper I pur• sue the second line. 8 a troublesome conclusion, which is tantamount to a sweeping scep• ticism about the external world. A crucial question regarding this argument is what justifies (2). One answer, which Barry Stroud examines at some length, runs as follows. 2 Suppose we know that if an exterience corresponds to real• ity, then it cannot be, and therefore is not, a dream. Let us also as• sume the closure of knowledge - namely, that if we know that p en• tails q, then if we know that p we must also know that q. Then, if we know that an exterience corresponds to reality, we must know that it is not a dream. But to say that we know that an exterience corre• sponds to reality is just another way of saying that it yields knowl• edge about the world. Q.E.D. Unfortunately, the fundamental assumption here is false, as Stroud is the first to admit. The world might perfectly well happen to be the way it appears to be in a dream, which is the same as to say that we need not be awake for our exteriences to correspond to reality. An amusing illustration of this point is G.E. Moore's anecdote about a certain Duke of Devonshire who once dreamt that he was speaking in the House of Lords and woke up to find that he was speaking in the House of Lords. 3 Even if untrue it is certainly coherent. Thus, Stroud's attempt at deriving (2) is unsound. Having conceded this failure, Stroud does not go any further in at• tempting to find the basic principles underlying (2). Instead, he seeks to show that this premise is indeed "an instance of a general procedure we recognize and insist on in making and assessing knowledge claims in everyday and scientific life". This he attempts to do by countering standard objections to Descartes' reasoning.4 Another argument for (2) is examined by Mark Steiner.5 Steiner considers it intuitively clear, and therefore a known fact, that if we know something about the world by way of an exterience, then this exterience cannot be, and therefore is not, a dream. By the closure of

2. Barry Stroud, The Significance ofPhilosophical Scepticism (Oxford: Ox• ford University Press, 1984), pp. 23-30. 3. G.E. Moore, Philosophical Papers (London: Allen and Unwin, 1959), p. 245. 4. Stroud, op. cit., chapters 2-7. 5. Mark Steiner, "Cartesian Scepticism and Epistemic Logic", Analysis, 39, 1979: pp. 38-40.