Moore's Proof And Martin Davies's Epistemic Projects

Abstract

In the recent literature on Moore's Proof of an external world, it has emerged that different diagnoses of the argument's failure are prima facie defensible. As a result, there is a sense that the appropriateness of the different verdicts on it may depend on variation in the kinds of context in which the argument is taken to be a move, with different characteristic aims. In this spirit, Martin Davies has recently explored the use of the argument within two different epistemic projects called respectively ‘deciding what to believe’ and ‘settling the question’. Depending on which project is in hand, according to Davies, the diagnoses of its failure—if indeed it fails—will differ. I believe that, by introducing the idea that the effectiveness of a valid argument may be epistemic project-relative, Davies has pointed the way to an important reorientation of the debates about Moore's Proof. But I wish to take issue with much of the detail of his proposals. I argue that Davies's characterization of his two projects is misleading (§1), and his account of their distinction defective (§2). I then canvass some suggestions about how it may be improved upon and about how further relevant kinds of epistemic projects in which Moore's argument may be taken to be a move can be characterized, bringing out how each of these projects impinges differently on the issue of the Proof's failure and of its diagnosis (§§3 and 4). In conclusion (§5) I offer an overview of the resulting terrain.

Notes

¹As a matter of fact, Moore meant his Proof to be an anti-idealistic argument—that is, an argument against those who deny that there is an external material world—and explicitly said it couldn't be used as an anti-sceptical one, viz. as an argument against those who think they can't know, or warrantedly believe, that there is an external material world. However, in another place [Coliva 2004] I show how, despite its author's intentions, the Proof, just as presented by Moore, can legitimately be read as an anti-sceptical argument as well.

²Besides the contributions by Wright [1985, 2000, 2002, 2003, 2004], Davies [1998, 2000, 2003, 2004, 2008] and Pryor [2000, 2004a, 2004b], which gave rise to, and have shaped the debate, see also Beebee [2001], Peacocke [2004: 112–15], Schiffer [2004], Brown [2005], Silins [2005], White [2006], Wright [2007], Coliva [2008a, 2008b] and Pryor [2008].

³One may be suspicious of the idea of ‘an abstract space of warrants' or, equivalently, of the notion of propositional warrant. Nothing in what follows really hinges on that, so long as one is happy with the distinction between having doxastic warrant for P—viz. thinking the thing to think, given one's available evidence—and being rationally answerable to what one takes to be the relations among warrants, even if one is mistaken about them. For, in such a case, where I talk about the abstract space of warrants one could simply replace my terminology with ‘doxastic warrant’. (Of course I cannot be responsible for Davies's terminology although I think he should not mind a similar replacement.) I am grateful to an anonymous referee for bringing to my attention the need to be clearer about these distinctions and to address the worry that talk of an abstract space of warrants may be spurious.

⁴As is well known, the kind of warrant Wright [2004] thinks we have for these general propositions is non-evidential, that is, an ‘entitlement’ in his terminology.

⁵This is not a temporal constraint but an epistemic one: the issue is whether or not warrant for (III) is needed for one's sense experience actually to provide warrant for (I).

⁶‘Thus, if the structure in the space of warrants is as Wright and the sceptic say that it is, then the use of Moore's argument in deciding what to believe fails to measure up to the overarching epistemic norm of that project […]. If the structure in the space of warrants is as Pryor's dogmatist says that it is then there need be no failure to measure up to the overarching epistemic norm if I use Moore's argument in deciding what to believe’[Davies 2008: 25].

⁷In Coliva [2008b] I present an intermediate position between Wright's and Pryor's.

⁸Let us ignore for present purposes that Wright [2004] thinks that one would nevertheless be entitled by default to assume (III).

⁹Pryor [2004: 364–5, 369] too distinguishes between a warrant's destruction and its rational unavailability to a given subject and calls the latter phenomenon ‘rational obstruction’.

¹⁰Beebee [2001] remarks that the phenomenon I call ‘rational unavailability’ wouldn't amount to Davies's first notion of transmission failure. However, it is important to note that here I'm not saying that Davies's alleged second kind of transmission failure can't count as a case of transmission failure because it isn't identical to the first one! What I am saying, rather, is that since his alleged second kind of transmission failure is a case where there is no (rationally available) warrant to transmit at all, it certainly can't count as a case of failure of warrant transmission in any reasonable sense.

¹¹In order to avoid possible confusions, it is important to stress that on Wright's account of Moore's Proof there is no failure of Closure. For the claim is merely that one's perceptual experience as such cannot give one a warrant to believe (I). To have such a warrant, one needs, besides a certain course of experience, also independent warrant for (III). Now, according to Wright, we do have such an independent warrant for (III), although he does not conceive of it as evidential. That non-evidential warrant—call it w∗—together with one's current experience as of a hand in front of one provides for an ordinary empirical warrant—call it w—for (I), which does transmit to (III) via the entailment. So, Closure holds, but what Wright is pointing out is that since w is not independent of w∗, just by having the appropriate kind of experience and running Moore's Proof one won't have a warrant to believe (III)—i.e. that there is an external world. I am grateful to an anonymous referee for bringing to my attention the need to clarify this point.

¹²Although, as we saw before, he unhappily views the phenomenon whereby doubt about (III) makes warrant for (I) rationally unavailable as an instance of a kind of transmission failure.

¹³Being principled is what sets it apart from mere open-mindedness. So an open-minded subject as to whether there is an external world could only be someone who (implausibly) has never obtained perceptual warrant for an ordinary empirical belief such as ‘Here is a hand’; or else, (more plausibly), someone who has never thought about the entailment between ‘Here is a hand’ and ‘There is an external world’ or, more generally, about the whole issue of whether our belief in the existence of an external world is warranted.

¹⁴It is difficult to conceive of such a contingent agnostic about the existence of an external world. One illustration may be provided by a subject who is rationally unpersuaded, so far, by both Moore's Proof, say, after reading Moore's paper as an assignment for his first year course in epistemology, as well as by the sceptical arguments against the existence of an external world so far reviewed in his course. However, such a subject is open to the idea that further developments of either argument (such as the ones recently provided by Pryor, or their counter on behalf of a sceptic lately advanced by Wright in response to Pryor's defence of Moore's Proof) which he can read of in the bibliography for his course could rationally persuade him to see things one way or the other. Given the difficulty of characterizing and of stabilizing such a position, it is particularly hard to see what effect Moore's Proof would have in ‘settling the question’ with respect to such a contingent agnostic.

¹⁵On the one hand, a philosophical sceptic will think that he has arguments which show that one can't warrantedly believe in the existence of an external world. On the other hand, being a sceptic as opposed to an idealist, he will also think that he has no warrant to conclude from that to the fact that the belief in the non-existence of an external material world is warranted. Moreover, I think he would insist that this isn't simply a provisional feature of the existent lines of inquiry. Rather, he will also think that no proof of the non-existence of an external material world can be provided in principle. For instance, a Cartesian sceptic will think that since, in principle, the content of one's perceptual experience is indistinguishable with respect to its cause, there is no way to acquire empirical evidence that one's beliefs on specific empirical objects are all produced by the interaction with a meddlesome scientist (or in a dream, or hallucination, etc.), and that they are, therefore, all false (this would of course be a weak form of idealism, since it would countenance, ex hypothesi, the existence of at least one scientist, brains, etc. Still it would impair the idea that there are ordinary empirical objects such as hands, chairs, human bodies and so forth). A Humean sceptic, in contrast, will think that since all empirical evidence in favour of or against specific empirical beliefs depends on the prior assumption that there is an external world, no empirical evidence can be acquired against (III), because it would in turn depend on assuming that piece of information. Thus, both Cartesian and Humean sceptics are robust and principled agnostics. To repeat, they believe that neither the belief in the existence nor in the non-existence of an external material world can in principle be warranted (and, a fortiori, known). I will presently come back to both forms of scepticism.

¹⁶As Stroud [1984: ch. 1] and Wright [1991] pointed out, to do so, according to Cartesian sceptics, we should first be able to prove that we are not dreaming (or envatted). That will require some kind of test. But our predicament is that we have no antecedent reason to exclude the hypothesis that we may in fact be dreaming of (or merely envattedly seeming to ourselves to be) carrying out any test we may devise to the end.

¹⁷Notoriously, Moore thought that his Proof could be replicated ad libitum just by substituting ‘Here is a hand’ with any similar, perceptually warranted, empirical belief.

¹⁸I am grateful to an anonymous referee for bringing to my attention the need to make this more explicit and thus to embark on the discussion of how conceiving differently of the structure of warrants would impinge on Moore's Proof's prospects of settling the question of whether there is an external world when directed to Cartesian and Humean sceptics.

¹⁹I would like to thank Sebastiano Moruzzi, Elia Zardini, two anonymous referees and especially Crispin Wright for extremely helpful comments on previous versions of this paper.