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With Fitelson and Waterman, I claim that Strevens’s conception of desperate and glorious rescues ends up hinging almost exclusively on the prior probabilities of h, which does not seem right, for several reasons. Fitelson and Waterman, in “Bayesian

Confirmation and Auxiliary Hypotheses Revisited: A Reply to Strevens”, criticize

Strevens’s solution to the Quine-Duhem-Ayer problem: a solution that I do not discuss in the body of this chapter20, as the distinction that Strevens makes does not affect the nature of ad hoc hypotheses, according to him. However, a brief digression into Strevens’s solution and Fitelson and Waterman’s critique of it will show how an assumption that Strevens makes in the solution to the Quine-Duhem-Ayer problem will bleed into his criteria for desperate and glorious rescues.

Fitelson and Waterman claim that Strevens makes a critical oversimplification when characterizing the problem, which causes other problems for Strevens’s theory. According to them, Strevens claims that:

e is equivalent to ~(h & a) (Fitelson and Waterman 294)

where e is the disconfirming evidence, h is the central hypothesis and a is the set of auxiliary hypotheses. Fitelson and Waterman’s issue with this simplification is that the simplification says that e consists of no more than the fact that h and a both aren’t true.

20

(Fitelson and Waterman 294) As a result of this, they argue, Strevens’s later claim that the relationship between the confirmation of h given e and the confirmation of a given e will depend on both the prior probabilities of h and a, as well as conditional probabilities such as the probability of a given h and h given a, is a false one. (Fitelson and Waterman 295) In fact, they claim, the simplification of the Quine-Duhem-Ayer problem makes the comparison of the confirmation of h given e and the confirmation of a given e just a comparison between the prior probabilities of h and a.21 This makes the disconfirming evidence irrelevant to the relationship between these two confirmations. (Fitelson and Waterman 295) And, as Fitelson and Waterman state: “[i]t seems clear to us that, in the original Q-D problem, the mere relationship between the priors of H and A should not by itself determine the relative support that E provides for H vs. A.” (Fitelson and Waterman 295) They continue the critique by saying:

We take Quine and Duhem to be asking the following question: In cases where H & A entails ~E, can the evidence E differentially confirm H vs. A – a posteriori – and, if so, how? This is not a question about the relative a priori plausibilities of H vs. A but rater a question about the a posteriori confirmational power of E to discriminate between H and A when H & A entails ~E. (Fitelson and Waterman 296)

In other words, Strevens’s solution of the Quine-Duhem-Ayer problem misses its mark. It misses its mark because it relies solely on the prior probabilities of H and A to

determine which ought to be thrown aside or modified given a certain piece of disconfirming evidence.

That Strevens’s account doesn’t adequately solve the Quine-Duhem-Ayer

problem is an issue for Strevens in a couple of ways. The first issue is that other attempts

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Strevens himself seems to be hinting at something like this in the two excerpts quoted in section IV of this chapter. (Strevens 535, 535-536)

to define ad hocness – such as Hempel’s – fall into the Quine-Duhem-Ayer problem and, thus, are not good definitions of ad hocness for the reasons stated in chapter 1, section IX. Therefore, it does not appear that Strevens can try to get out of the problem via any of the pathways that the other, failed, attempts take.2223

The other way that Fitelson and Waterman’s critique is problematic for Strevens occurs as a result of Strevens’s distinction between glorious and desperate rescues. If the confirmation of h given e and the confirmation of a given e are based merely on the prior probabilities of both h and a, then whether a rescue is glorious or desperate will also be based on these prior probabilities. This is a problem because it would seem that, given a relatively well-established theory without serious rivals, any rescue of it would be a glorious – and, therefore, justified or, at least, permissible – one. This is not a happy outcome, for it seems perfectly plausible to think that there could be cases (such as the Ptolemy case) where, because of disconfirming evidence, the introduction of a hypothesis into a well-established theory without any serious rivals ought to be desperate,

unjustified. However, this sort of outcome looks very improbable, given the dependence of Strevens’s account on the prior probabilities of h and a. Alternatively, it would seem that a newly presented theory, introducing a hypothesis because of disconfirming

22

Fitelson and Waterman claim that the likelihood-measure l is a better Bayesian measure of confirmation and Bayesian accounts using l can better deal with the Quine- Duhem-Ayer problem. I will not evaluate these claims here.

Fitelson, Branden and Waterman, Andrew. “Comparative Bayesian Confirmation and the Quine-Duhem Problem.” The British Journal for the Philosophy of Science, forthcoming.

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Strevens has published a response to Fitelson and Waterman. However, this response concentrates on another part of their critique of his paper and does not really address the issue raised, above. Fitelson and Waterman note this as well, in a response to Strevens’s response. (Fitelson and Waterman, forthcoming)

evidence, would almost always be committing a desperate rescue. This, too, seems an unfortunate consequence.

To have ad hocness reduce to whether or not a hypothesis is being introduced into a well-established theory or a non-well-established theory because of disconfirming evidence creates two negative consequences. Firstly, that there are good and bad ad hoc acts does not map on to scientists’ use of ad hoc. Secondly, as ad hocness is equivalent to the prior probabilities of theories, the vice of ad hocness just refers to the modifications, due to disconfirming evidence, to a theory with a low prior probability and the virtue of ad hocness refers to the relevant modification to a theory with a high prior probability. This is to place the emphasis, and to move the label ‘ad hoc’, on the theories themselves, without taking into account the particular hypothesis being accepted. Yet, this is

precisely where the emphasis, and the label ‘ad hoc’, should be placed. And, Fitelson and Waterman have pointed to the same problem of emphasis in Strevens’s attempt at a solution to the Quine-Duhem-Ayer problem.