In Can We Do Without Pragmatic Encroachment?, I argued that the various phenomenon that pragmatic epistemological theories were trying to explain were primarily due to the pragmatic nature of belief, not the pragmatic nature of justification. A large part of Fantl & McGrath’s response to this is to argue that a pragmatic theory of belief isn’t sufficient to derive principles like this one, which they take to be central to a pragmatic epistemology.
(JJ) If you are justified in believing that p, then p is warranted enough to justify yoy in φ-ing, for any φ.
This isn’t actually one of the principles they say I can’t derive, but it’s in the ballpark. And it’s relevant because (a) the principles they think I should be able to derive are stronger than (JJ), and (b), (JJ) is false. I think the argument against (JJ) in Can We Do Without Pragmatic Encroachment? is pretty good, but it can be simplified. Here’s a much simpler version. The following is all true of an agent S.
- She knows that p and q are independent, so her credences in any conjunction formed out of p, ¬p and q, ¬q are products of the credences in the conjuncts.
- Her credence in p is 0.99, just as the evidence supports.
- Her credence in q is also 0.99. This is unfortunate, since the rational credence in q given her evidence is 0.01.
- She has a choice between taking and declining a bet with the following payoff structure.
- If p ∧ q, she wins $100.
- If p ∧ ¬ q, she wins $1.
- If ¬ p, she loses $1000.
- The marginal utility of money is close enough to constant that expected dollar returns correlate more or less precisely with expected utility returns.
As can be easily computed, the expected utility of taking the bet given her credences is positive, it is just over $89. Our agent S takes the bet. She doesn’t compute the expcted utility, but she is sensitive to it. That is, had the expected utility given her credences been close to 0, she would have not acted until she made a computation. But from her perspective this looks like basically a free $100, so she takes it. Happily, this all turns out well, since p is true. But it was a dumb thing to do. The expected utility of taking the bet given her evidence is negative, it is a little under -$8. So she isn’t warranted, given her evidence, in taking the bet.
I also claim the following three things are true of her.
- p is not justified enough to warrant her in taking the bet.
- She believes p.
- This belief is rational.
The argument for 1 is straightforward. She isn’t warranted in taking the bet, so p isn’t sufficiently warranted to justify it. This is despite the fact that p is obviously relevant. Indeed, given p, taking the bet strictly dominates declining it. But still, p doesn’t warrant taking this bet.
The argument for 2 is that she has a very high credence in p, this credence is grounded in the evidence in the right way, and it leads her to act as if p is true, e.g. by taking the bet. It’s true that her credence in p is not 1, and if you think credence 1 is needed for belief, then you won’t like this example. But if you think that, you won’t think there’s much connection between (JJ) and pragmatic conditions in epistemology either. So that’s hardly a position a defender of Fantl and McGrath’s position can hold.
The argument for 3 is that her attitude towards p tracks the evidence perfectly. She is making no mistakes with respect to p. She is making a mistake with respect to q, but not with respect to p. So her attitude towards p, i.e. belief, is rational.
These three points entail that (JJ) is false, since S provides a counterexample. So I don’t think it’s a bad thing that you can’t derive principles like (JJ), or stronger principles, from my theory of belief. The derivation doesn’t work because my theory of belief is true, and those principles are false!