Abstract
Very possibly the most famously intractable epistemological conundrum in the history of modern western philosophy is Descartes’ argument from dreaming. It seems to support in an irrefutable way a radical scepticism about the existence of a physical world existing independent of our sense-experience. But this argument as well as those we discussed in the last chapter and many others of the same kind rest on a conflation of evidence and confirmation: since the paradoxical or sceptical hypothesis has as much “evidence” going for it as the conventional or commonly accepted hypothesis, it is equally well supported by the data and there is nothing to choose between them. By this time, however, we understand very well that data that fail to discriminate hypotheses do not constitute “evidence” for any of them, i.e., that “data” and “evidence” are not interchangeable notions, that it does not follow from the fact that there is strong evidence for a hypothesis against one or more of its competitors that it is therefore highly confirmed, and that it does not follow from the fact that a hypothesis is highly confirmed that there is strong evidence for it against its rivals.
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Notes
- 1.
Descartes (1984, p. 14).
- 2.
Or if not false, then groundless. The widely reported (and however implausible) case of the Duke of Devonshire, who dreamt that he was giving a speech in the House of Lords when he was in fact giving a speech in the House of Lords, shows that a belief may be true yet without the right sorts of reasons to support it.
- 3.
Stroud (1984), passim.
- 4.
Descartes puts the point in just this way in the Sixth Meditation: “The first [general reason for doubting] was that every sensory experience I ever thought I was having while awake I can also think of myself as sometimes having while asleep; and since I do not believe that what I seem to perceive in sleep comes from things located outside me, I did not see why I should be more inclined to believe this of what I think while awake” (Descartes 1984, p. 53).
- 5.
Stroud (1984, p. 32), our italics. Similarly, Williams (2001, p. 75), says: “To get to radical skepticism [‘the thesis that our beliefs are completely unjustified’], the sceptic must not concede that his possibilities are remote. He must argue that they are as likely to be true as what we ordinarily believe. This is what he does. His point is that his bizarre stories about Evil Deceivers and brains-in-vats are just as likely to be true as our ordinary beliefs given all the evidence we will ever have. In the case of the external world, all the evidence we will ever have comes from our sensory experience; … in every case, he will claim, all the evidence we will ever have radically undermines what it would be true or even justifiable to believe” (his italics). It follows, Williams thinks, that we have no reason to believe that we are awake, given that we might be dreaming. This is a non-sequitur. It turns on the near-universal conflation of “evidence” with “justification”. Granted that although there is little evidence properly so-called in the radical skeptical cases, we might still have very good reasons for belief.
- 6.
In fact, we are asleep roughly a third of the time, and dream roughly a fifth. While the role of sleep, still less that of dreams, is not yet fully understood, it is nonetheless clear that in the ordinary course of events, nutrition, among other bodily requirements, can (except when hooked to a feeding tube) be met only when we are awake. Not all of us can sleep, hence dream, all of the time (though some friends of ours make a very good pretense). The general contingencies of survival demand that we be more often awake. Indeed, horses and goats sleep only two to four hours a day, apparently to maximize their foraging time and minimize their vulnerability to predators. See Anch et al. (1988).
- 7.
In our view we are “tricked” into believing we are awake when in fact we are asleep, not so much by the fact that our dreaming experiences are “qualitatively indistinguishable” from our conscious experiences, for often they are not, as by the fact that we understandably tend, other things being equal, to believe that we are awake (even when we are not) as a heuristic rule.
- 8.
The move is standard in the Cartesian secondary literature. Thomson (2000, p. 33), for example. Descartes’ point “…is rather that we have no internal evidence or criteria which surely distinguishes dreaming and waking experience”. From which it follows that “Any particular experience could be a dream”, i.e., we would have no reason to believe of any particular experience that it was not a dream.
- 9.
It is explicit in Descartes, implicit in the arguments of many of those who think that the argument from dreaming is sound, that the reasons for our belief that we are awake must be “conclusive”, i.e., cannot themselves be doubted. In the traditional vocabulary, whatever qualifies as a “reason” must be able to serve as a foundation for the rest of our knowledge. But as we indicated in Chap. 1, an important premise of this monograph is that what we believe on the basis of what we experience has no “foundation” in this sense. It is invariably uncertain. The task is not to evade this fact, but to provide a way of distinguishing between well- and poorly-grounded beliefs, even to the point of quantifying the degree to which they are well- and poorly-grounded. Whether it qualifies as “knowledge” or not, it is more than enough to support the claim that science provides us with very well-grounded beliefs about the physical world.
- 10.
Salmon (1990, p. 270).
- 11.
Ibid., p. 264.
- 12.
In this case, as in many others, formal must be distinguished from causal simplicity. As Miller (1987, p. 247), reminds us, “by adding a variety of novel propositions…evolutionary theory reduces the formal simplicity of science. [But] an enormous gain in causal simplicity results. For a variety of regularities which ought, according to all rival frameworks, to have causes only have causes once the evolutionary principles are added”.
- 13.
Although again, his argument is more persuasive on causal than on formal grounds. See Kuhn (1959, pp. 169–171). We are following the conventional wisdom, of course, in claiming that they are empirically equivalent, for in fact they are not.
- 14.
See Brown (1991) for an account of this and other apparently data-independent plausibility arguments.
- 15.
See Galileo (1974, pp. 66–67). In preparation for his thought-experiment, Galileo had already noted (p. 64) that “where we lack sensory observations, their place may be supplied by reasoning which is no less capable of understanding the change of solids by rarefaction and resolution than [the change of] tenuous and rare substances by condensation”.
- 16.
Norton (2002, p. 44).
- 17.
A point apparently not lost on Descartes, for on his account dream images could only have been derived from prior waking experience (see the following footnote and, and for an earlier reference in the First Meditation—“it must surely be admitted that the visions which come in sleep are like paintings, which must have been fashioned in the likeness of things that are real”—Descartes (1984, p. 13). He has several reasons for moving rather quickly to the supposition of an Evil Demon; this is one of them.
- 18.
As part of his eventual response to skepticism concerning the existence of objects independent of our ideas of them, Descartes essays his own plausibility argument for assigning the “object hypothesis” a higher prior. On this hypothesis, “I can … easily understand that this is how imagination comes about … and since there is no other equally suitable way of explaining imagination that comes to mind, I can make a probable conjecture that the body exists”. He goes on, of course, to say that “this is only a probability” and “not the basis for a necessary inference that somebody exists”, but continuing interest in the argument from dreaming does not derive from his insistence on certainty, but rather from the more general claim that we can have no reason not to believe that we are dreaming. See Descartes (1984, p. 51).
- 19.
However deeply ingrained it is. J.L. Austin, among many others, thinks that the only way to avoid the conclusion is to deny the premise. In his view, there are all kinds of important differences between waking and sleeping experiences. Thus he writes in Austin (1962, p. 48): “I may have the experience … of dreaming that I am being presented to the Pope. Could it be seriously suggested that having this dream is ‘qualitatively indistinguishable’ from actually being presented to the Pope? Quite obviously not”. End of discussion! Here as so often in philosophy and elsewhere, it is not the premise that is to blame but the inferential pattern, use of which is subsequently made. Our aim is to enlarge the usual kit-bag to include patterns of uncertain inference that are not typically combined.
References
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Bandyopadhyay, P.S., Brittan, G., Taper, M.L. (2016). Descartes’ Argument from Dreaming and the Problem of Underdetermination. In: Belief, Evidence, and Uncertainty. SpringerBriefs in Philosophy(). Springer, Cham. https://doi.org/10.1007/978-3-319-27772-1_10
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