Philosophy, Film, Politics, Etc.

Friday, April 15, 2011

Devitt and the A Priori

I've just looked at Michael Devitt's paper, "Naturalism and the A Priori." He claims that epistemological naturalism cannot accommodate the a priori. According to epistemological naturalism, he says, all knowledge is justified by experience and nothing else. Since a priori knowledge is, by definition, knowledge which does not rely on empirical evidence for its justification (regardless of whether or not it is obtained by experience), then a priori knowledge is incompatible with epistemological naturalism. And since he is an epistemological naturalist, he claims there cannot be a priori knowledge.

I won't go through all of his arguments, which are largely critical: he is primarily concerned with criticizing various arguments for the a priori, though he does lay out two arguments against it: the first is that the notion lacks motivation; the second is that it is too obscure to be taken seriously. (This latter argument reminds of one of Mackie's argument against moral realism: that the notion of objective morality is just too bizarre to be lent any credence.)

My concern is that the way Devitt frames the debate seems questionable. His primary strategy is to focus on the issue of justification: we all know what it means to have empirical knowledge, because we know what it means to learn from experience. Experience justifies our beliefs. And, Devitt says, knowledge is justified true belief. So why claim that some justified true beliefs aren't justified by experience? What could they be justified by, if not experience?

When framed that way, his argument has a good deal of persuasive force, even if you don't agree with it. But why frame it this way? Why assume that all knowledge is justified true belief? If a priori knowledge is not the sort of knowledge that could be justified, even in principle, then Devitt's entire argumentative strategy is inappropriate. The question is, what sort of knowledge is it?

My proposal: A priori knowledge might be knowledge of a certain class of rules which can be defined as those rules whose existence depends only on their being known. The knowledge of such rules cannot be justified in principle, because the existence of what is known depends only on the fact that it is known. So, for example, "2+2=4" is knowable a priori, in the sense that it is a meaningful proposition which has meaning only in so far as it is known--which is to say that what is known is an aspect of the knowing, and not distinct from it.

This is surely an incomplete picture of a priori knowledge. But I find something compelling about it.

See follow-up: Procedures and the A Priori