Читать книгу This Is Epistemology - J. Adam Carter - Страница 18

^1.25 The infinitist insists that a given belief is justified iff that belief is supported by an infinite set of non‐repeating justifiers. One standard complaint about this proposal is that it puts justification out of our reach because – given the kind of cognitively limited creatures we are – we simply don't have an infinite set of justifiers available to support our beliefs. If this is right, infinitism doesn't provide us with a non‐skeptical response to the regress problem. Here's the argument in outline – that is, the Argument from Finite Minds:

Argument from Finite Minds

P1. You have a finite number of beliefs.

P2. Nothing could be a justifier that supports your beliefs at any given time unless it is itself a belief.

C1. You have a finite number of justifiers that support your beliefs at any given time.

P3. Infinitism tells us that a belief is justified only if supported by an infinite set of non‐repeating justifiers.

C2. Infinitism implies that none of your beliefs could be justified.

An initial line of response the infinitist could offer here would be to contest the relevance of P1 to the truth of infinitism. As this line of thinking goes, infinitism is a thesis about epistemic justification “in and of itself” and not merely about justification that's accessible to the kinds of minds that humans happen to have.¹⁷ Accordingly, what infinitism says about epistemic justification is not beholden to anything we might discover about human minds and their distinctive limitations. Leaning on this point, though, would not be very good strategy for the infinitist, all things considered. After all, even if the reply is granted, a counterreply awaits: infinitism still implies that no human beliefs can be justified. Thus, infinitism is not a non‐skeptical response to the regress problem when it comes to the very kind of justification we're most interested in: the kind we humans (with whatever limitations we have) are capable of attaining.

^1.26 A more promising line of response to the Argument from Finite Minds is that it rests on a mistaken picture of justifiers. While a justified belief might be a perfectly good justifier, maybe – and contrary to P2 – not every justifier is another justified belief.¹⁸ For instance, if we understand justifiers as justified beliefs or available reasons that an agent could cite if challenged, the set of justifiers might be larger than the set of beliefs. It might (as the infinitist says) be infinite even if what we actually believe is not.

^1.27 This might seem like a decent line for the infinitist to press, though it invites a new kind of problem. Consider that to respond to the Argument from Finite Minds the infinitist has had to broaden the class of justifiers to include things that aren't now believed but are nevertheless available in some sense. Perhaps these are things that we would accept or believe and cite in support of our beliefs if challenged or asked for a justification.¹⁹ If this line of reply could be made to work, then it would free the infinitist up to deny that justification requires having more beliefs than we really have.

^1.28 At this same time, though, if the set of justifiers that would justify the beliefs you hold now could consist not entirely of things that moved you to form the beliefs in the first place, then a new kind of worry surfaces, which is that the infinitist would have no way to distinguish justification from mere rationalization (e.g. citing reasons that weren't your actual reasons, but which you might nonetheless cite if pressed).

^1.29 One strategy in response to this kind of worry that has been pursued by Peter Klein (2005, pp. 135–136) is to clearly differentiate the infinitist's demands on two distinct kinds of epistemic justification: propositional justification (roughly, the kind of justification you have for a proposition if it would be reasonable for you to believe it) and doxastic justification (roughly, the kind of justification you have for beliefs held on the basis of reasons you're propositionally justified in believing²⁰). For the infinitist, the proposition expressed by B1 (i.e. rental prices will continue to increase in London in the coming year) is propositionally justified for you just in case there is available to you at least one infinite non‐repeating series of propositions (or reasons) such that R1 is a good reason to believe B1, R2 is a good reason to believe R1, R3 is a good reason to believe R2 … and so on.²¹ But to be doxastically justified in believing B1, the mere fact that B1 is propositionally justified for you is not sufficient. A further necessary condition is that you must have appropriately provided, as Turri (2013, p. 792) puts it, “enough reasons along at least one of the infinite non‐repeating series of reasons, in virtue of which [sic. your belief] is propositionally justified for you, to satisfy the contextually determined standards.” Regarding “contextually determined standards”: in short, the idea is that providing several reasons (from the infinite series that is available to you) may suffice for doxastic justification in an epistemically friendly setting, whereas in the context of a hostile interrogation, say, doxastic justification might require that you provide (say) 10 or 35 of them. But you are not required to provide an infinite series of reasons.

^1.30 By drawing this distinction – in particular, by insisting that infinitist propositional justification is not sufficient for infinitist doxastic justification – the infinitist looks initially to be in a position to sidestep the kind of rationalization worry noted above. After all, once the distinction is drawn in the way Klein draws it, your actually citing certain reasons (from the relevant infinite non‐repeating series) is doing some of the heavy lifting in accounting for your belief's doxastic justification.

^1.31 However, it's hardly the case that the infinitist is in the clear simply by drawing the distinction noted. To appreciate this point, consider the following two infinite series:

Series 1: R1, R2, R3, R4, R5 …

Series 2: R1, R3, R2, R4, R5 …

Assume that these two series contain the same infinite number of reasons, but in a different order; while there is no reason in Series 1 that does not occur in Series 2, and vice‐versa, Series 1 might suffice to justify your belief while Series 2 does not. (After all, R2 might be a good reason to believe R1, but R3 might not be.²²)

^1.32 As Podlaskowski and Smith (2011) have argued, this fact – in short, that “ordering matters” – turns out to be relevant to whether Klein's strategy of response to the Argument from Finite Minds ultimately works.²³ Podlaskowski and Smith's objection proceeds as follows (pp. 521‐2): even if it is granted that we have an infinite series of beliefs available to us, we don't have such a series available to us in the right order!

^1.33 This is initially a perplexing point. Why, exactly, would they think this? Their reasoning has two steps. The first is to point out that Klein is by his own lights committed to thinking about the notion of “availability” present in the infinitist's account of propositional justification in terms of dispositions²⁴ – viz. that every reason in the infinite chain is one that you'd be disposed to cite at an appropriate point. While Klein doesn't think you have to actually possess (for some reason in the infinite chain, R) the first‐order disposition to cite R at the appropriate point, you must at least possess the (second‐order) disposition to form the relevant first‐order disposition to cite R at the appropriate point in the series.

^1.34 But, as Podlaskowski and Smith (2011) argue, you (constituted as you are) don't actually have that second‐order disposition! As they put it:

Faced with an infinite chain of reasons to cite, it is more likely that, at some point along the chain, S has the disposition to offer a guess or become bored with the whole enterprise (instead of having the epistemically credible disposition to continue citing reasons). There is good reason to think, then, that for a great many cases, S does not possess the relevant second‐order dispositions whatsoever.

Some infinitists have attempted to get around this worry by appealing to a rather weak notion of a second‐order disposition that is needed for the relevant reasons to count as “available” to cite in the right order;²⁵ for instance, as Turri says, “even if it's more likely that at some point you'll fail to correctly cite the next reason in the chain, due to a performance error [e.g., boredom], it doesn't follow that you lack any disposition to correctly cite the next reason” (p. 794).

^1.35 Taking a step back from this dispute, we can see a dilemma materializing for the infinitist. If the sense in which the relevant reasons in the infinite series must be “available” to you (for propositional justification to be secured) is understood so weakly that cases like Podlaskowski and Smith's will not be problematic, then it's perhaps too weak for the availability of such an infinite series to contribute in a suitably significant way to (what is, according to the infinitist) doxastic justification.²⁶ However, if “availability” is understood strongly enough that the infinite series available to you plausibly contributes to your doxastic justification, then objections like Podlaskowski and Smith's begin to look problematic again.

^1.36 Let's set aside the Argument from Finite Minds and consider an entirely different kind of worry that infinitism faces, one that doesn't concern issues to do with human cognitive limitations. To this end, consider that one of the main motivations for infinitism is a desire to satisfy this principle:

Principle of Avoiding Arbitrariness: for all propositions, x, if x is warranted for a person, S, at t, then there is some reason, r1, available to S for x at t; and there is some reason, r2, available to S for r1 at t, etc., and there is no last reason in the series.

(Klein 2005, p. 136)

Infinitists want to satisfy this principle in the main because they think a belief that isn't supported by such a set of non‐circular reasons will be held on the basis of a foundational belief that is itself arbitrary, since no further belief would support it.

^1.37 If a belief is supported by further beliefs that ultimately turn out to be unfounded, it can seem that the whole chain of beliefs is unfounded. For some beliefs, however, it doesn't seem that many reasons, if any, are required. Consider, for example, beliefs about your present sensations (e.g. your belief that your nose itches or that your head aches), beliefs about your present thoughts (e.g. your belief that you are currently thinking of New Jersey), and your perceptual beliefs (e.g. your belief that the page you're reading right now is covered with black marks). Even if you cannot think of any independent considerations to offer in support of these beliefs, these beliefs look like good candidates for justification and knowledge. Consider the belief that you're in pain, for example. It wouldn't be an arbitrary thing to believe if it's formed in response to the kinds of experiences you'd have when touching a hot iron or skinning your knee.²⁷

^1.38 One of the oddities of the infinitist view is that it will try to account for the fact that the beliefs just mentioned can be justifiably held by positing an infinite series of reasons where the reasons it posits seem to be more epistemically problematic than the belief that they're supposed to support. If you believe that you're in pain and someone asks you to identify a good reason to think that you are, you might come up with something. You might say that you're sweating and showing the standard physiological responses to pain, and you might point out that you need painkillers. But even if we have these reasons, they might seem otiose.

^1.39 While considerations such as these might be good reasons for someone to believe that you're in pain, why would you need them to justifiably form this belief? How could such considerations account for the fact that it would be right for you to be much more confident that you're in pain than you are confident that any of the supporting reasons you've just mentioned are true?

^1.40 This general idea is captured famously by Ludwig Wittgenstein in his posthumous On Certainty (1969) in the following passages, where Wittgenstein suggests it would not be promising to adduce what is less certain to one in the service of supporting what is more certain to one.

My having two hands is, in normal circumstances, as certain as anything that I could produce in evidence for it. That is why I am not in a position to take the sight of my hand as evidence for it.

(OC, §250)

If a blind man were to ask me “Have you got two hands?” I should not make sure by looking. If I were to have any doubt of it, then I don't know why I should trust my eyes. For why shouldn't I test my eyes by looking to find out whether I see my two hands? What is to be tested by what?

(OC, §125)

Wittgenstein, in making these remarks, is taking the proposition that one has hands to be (like the proposition that one is in pain) the sort of thing that you know if you know anything at all.²⁸ And such bedrock certainties (what Wittgenstein calls “hinges”) are difficult to support by appealing to any kind of evidence that's more certain to one than these bedrock certainties themselves.

^1.41 At some point – in the case of what is most obvious to us – it seems that the ability to just see that something is so using the finite reasons at hand should be enough for knowledge and justification if these epistemic standings are attainable. The intuitive force of this point is hard to ignore, and if this point is conceded, then it's unclear why there would have to be some further infinite set of reasons waiting in the wings for our beliefs to constitute knowledge or to be justifiably held. If you can just see that something is true, it wouldn't be right to describe your belief as being held on an arbitrary basis.