It’s been a while, but let’s get back to talking about the Degrees of Belief book. Next up is Keith Frankish on Partial Belief and Flat-Out Belief.
Frankish starts from the worry that should be familiar to anyone following the posts on this book: there is a tension between categorical (flat-out) belief and degrees of belief. After introducing this duality, and its concomitant tension – which I won’t do again – Frankish moves to considering a number of ways of cashing out what the relationship is between categorical and graded belief. He first considers graded belief as derivative of full belief. Then he considers a reduction going the other way: reducing full belief to partial belief. Then he considers two strategies of keeping both concepts as real parts of a view of belief. He ends with some remarks on the relationship between belief and action.
Maybe it’s being at the LSE, doing all this decision theory, but I just take it as uncontroversial that degrees of belief are a necessary part of any model of belief. So for me, the question boils down to “Can full beliefs be reduced to graded belief?” Earlier papers we’ve discussed already talked about the “Lockean Thesis” which is, broadly, the view that full belief is just sufficiently strong partial belief. All the work is to understand what “sufficiently strong partial belief” means. Frankish worries that understanding full belief in this way makes full belief explanatorily idle. I’m not super worried about this. I don’t think I share Frankish’s strong opinions on there really being important, distinct, work we want our full belief concept to be doing for us. I guess this reflects our differing backgrounds: I am more focussed on decision theory, Frankish comes from a philosophy of mind background.
But I think I can grant Frankish that we want a genuine, useful concept of full belief and still maintain that it reduces to degree of belief (somehow). I think full belief reduces to partial belief in the same way that thermodynamics reduces to statistical mechanics: they are descriptions of the same thing at different levels. One can accept this reduction, and still maintain that thermodynamics does useful explanatory work in some contexts. Likewise, one can accept that full belief reduces to partial belief, and still maintain that, in some contexts, full belief is useful for explanation.
I don’t know whether Frankish would actually disagree with any of the above, since I take his discussion of his own view to be in line with this reductionist story I have sketched. Indeed, in responding to criticisms of his view, Frankish talks in terms of full and partial beliefs being on different “levels”. He basically says that full beliefs and partial beliefs operate at different levels of explanation, in the same way that a physical explanation and an intentional explanation of an action are explanations of the same thing at different levels (pp. 88–9).
I don’t think I’ve really done justice to Frankish’s paper. I have not really discussed much of the interesting argument in the paper, but rather used it as a starting point to expound my own view. I expect this will happen with other papers in this collection too.