Which prior assumptions

Epistemology is difficult. (Remember that long discussion between G and Ben the other day? Shop talk. Difficult shop talk.) This morning I was trying to figure out the meaning of a comment by Josh Rosenau on Jerry Coyne’s post last week on Dawkins and accommodationism and I followed a link to a three-year-old post by John Wilkins on agnosticism. It’s good, and interesting, and much of it I don’t understand. This for instance:

Probabilities are based in this case on prior assumptions – one uses Bayes’ theorem to determine whether or not the hypothesis under test is likely to be true, given other assumptions we already accept. And here is where the problem lies – which assumptions? To adopt and restrict one’s priors to scientific assumptions is question begging. You in effect eliminate any other conceptual presuppositions from being in the game. This has a name in philosophy – positivism. It is the (empirically unsupportable) claim that only scientific arguments can be applied. As Popper noted, this is self-refuting. You cannot prove the basic premise of your argument that only provable (or, let’s be generous, supportable) claims should be accepted. As this is not a supportable claim in itself, you have contradicted your own position.

You cannot prove the basic premise, but can you support it? If the basic premise of your argument is that only supportable claims should be accepted, can you support that premise, and is supporting it enough? Do you have to prove it? If support is enough then you haven’t contradicted your own position, right?

An agnostic says that since one can make God likely or unlikely by shifting one’s priors appropriately, at the level of metadiscourse there is nothing that can decide between them. As it happens, I share most of Dawkins’ assumptions about how knowledge is gained, and it does seem to me that God is unnecessary in scientific reasoning, but I cannot show, nor can he or anyone else, that scientific reasoning is all that should or can ever be employed. And that is not “fence sitting” but a recognition of the limits of this kind of metalevel argument…[A]ll I am doing is admitting that, at the level of philosophical discourse, I can neither affirm nor reject these entities, and that what makes them likely or unlikely depends crucially on the priors that one accepts.

And, if I understand him correctly, ‘at the level of philosophical discourse’ you can’t say one prior is better than another (or you can say but you can’t prove or demonstrate or even support the claim that). Is that right? Is that what he means, and if it is, can it be right? Does it all depend on careful wording (you can’t prove, but you can do something short of proving) or does it say something real and significant and compelling?

The Proofs of God that Dawkins reviews in the book are not decisive, true. Neither are the Disproofs of God. Dawkins is confusing personal conviction with formal demonstrability. He may be convinced there is no God. But he cannot demonstrate that. At best he can set up the dialectic conditions in which his conclusion is shown to be justified. But, and here’s the kicker, so can theists. It’s all about what prior assumptions you feed into Bayes’ Theorem.

Yes, I get that…but some prior assumptions are more reasonable than others – which one can’t prove or demonstrate, but one can support it. One can point out what works and what doesn’t – in the world and circumstances we are familiar with. Sure maybe there’s a metalevel where none of that applies, but for our purposes, here and now, where we can only go with our best information…some prior assumptions are more reasonable than others.

I suppose that’s why I find myself saying ‘yes all kinds of things might be true but without evidence there’s no good reason to believe they are true’ so often these days. Variations on agnosticism are popular when theists meet Militant New atheists.

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