Through-going subjective Bayesianism as a solution to the problem of scepticism

A common argument for the existence of God is that there is something rather than nothing. There are many good replies to this argument, but one of the more sophisticated challenges our sense that ‘nothing’ is the ordinary state of things and ‘something’ is an exception that needs explanation. There is an enormous, uncountably infinite plurality of ways the world could be. The ‘nothing’ world is simply one of these ways, and no more inherently ‘natural’ than the others. Why must the initial state of the universe be nothing unless we can give a reason otherwise?

We might talk then of the ‘nothingness is natural’ fallacy in relation to the initial conditions of universes. Scepticism seems to me to commit a variant of this fallacy in relation to epistemology. The set of permissible beliefs is assumed to start empty or near-empty, and then we have to fill it. A very low probability judgement for all statements is assumed to be the real correct default. Any exception is in need of justification.

There is an alternative view of epistemology that does away with scepticism. I see it as, broadly speaking, a development of G.E. Moore’s argument against scepticism to a whole epistemology by way of subjective Bayesianism, though this might simply be reading my own ideas into Moore’s work. It is a development of subjective Bayesianism into a full epistemological standpoint, a kind of alternative to coherentism and foundationalism, or a dissolution of the questions they attempt to dissolve, depending on how you look at it. The view goes like this. There are no rationality requirements beyond consistency on the initial assignment of priors. Inductive rationality only governs the updating or changing of our beliefs and does not impose any constraints on our initial beliefs beyond consistency requirements of the kind given by the Dutch book argument. The real province of normative epistemology is purely the assessment of changes in probability assignments. The demand for some ultimate justification of the initial judgements is an illusory over-generalisation from the practice of justifying changes in levels of belief.

On the subjective understanding of probability, we do, after all, have to have some priors, and there is no known principled way of assigning them. Thus we arrive at some rather simple anti-sceptical proofs. For example, mirroring Moore’s proof of an external world, we simply observe that our prior belief in an external world is rather high, and nothing has decreased it.

So why does the problem of scepticism appear to be a real problem? Over-generalisation. If I tell you that Susie is a lecturer in mathematics, you might ask how I came to know that, because you adjudge that it is very unlikely that it’s simply built in to my priors that Susie is a lecturer in mathematics. This is true of basically all statements worth talking about outside a philosophical context, thus we get into the habit of thinking in terms of justifying our beliefs. When I then tell you that I believe there is an external world, and you ask how I know this, and I cannot give an adequate reply, it appears something is wrong. Really though this is a sort of illusion, all we are ever doing is justifying why we have decreased or increased our credence. Since your a priori belief that Susie is a mathematician is presumably low you need to explain why it has risen but the same is not true of belief in an external world, or causation.

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