comment by Rob Bensinger (RobbBB) ·
2013-01-16T16:44:02.304Z · LW(p) · GW(p)
I think both of our definitions are reasonably common, and that both are also somewhat misleading. I recommended mine partly because I've seen it from a lot of sources, e.g.:
Penguin Dictionary of Philosophy, entry on a priori: "'It can be known a priori that p, if anyone whose experience is enough for him to know what "p" means, requires no further experience in order to know that p.'"
Allen Wood, leading Kant scholar: "A proposition is known a priori when knowledge of it does not depend in any way on the specific contents of experience, when any experience that would suffice to enable us to entertain the proposition would also be sufficient to give us knowledge of its truth."
So I think this 'quasi-analytic' definition is the more traditional one, though perhaps it doesn't fully capture modern usage. I also recommended it because I find the dispute over analyticity more philosophically interesting and deep than the dispute over what counts as sense-data. 'Is the experience of reasoning a sensory experience?' seems more obviously terminological than 'Is 2+2=4 true purely in virtue of its meaning?'
You say that the ambiguity of the term 'senory experience' "has been at the heart of philosophical discussion about the a priori", but I think it's been mostly a blind-alley, and that the really substantive debates about the a priori have instead concerned the nature of justification in the absence of any experiential evidence, including memory, phenomenological introspection, telepathic insight, divine revelation... -- all of which fail to be conventionally 'sensory'.
Or perhaps: Absent any experiential evidence aside from my experience with natural chains of reasoning and inference...?
Here, I think, is where the heart of the dispute over the a priori lies: The question, not of whether our reasoning chains and intuitions are 'sensory,' but over whether they afford a categorically different kind of epistemic justification than does induction. The question is not 'When I reason from the Peano axioms to 2+2=4, is my reasoning sensory?'. Instead, the question is 'When I reason from the Peano axioms to 2+2=4, is my warrant or justification contingent upon inductive generalizations like "In the past, my mathematical reasoning has tended to be accurate"?' Is it ever the case that I just know X, because of the character or dynamics of my reasoning, and not purely because of my empirical grounds for deeming my reasoning reliable? Huge swathes of epistemology stand or fall with this question.
Still, your point stands that the terminology seems redundant if we can't distinguish a-priori knowledge from analytic. Bruce Russell suggests this analysis, which is more careful than my definition above:
Perhaps there are two ways belief in a proposition can be justified a priori. First, a person might have an intuition that a proposition like “bachelors are unmarried” is true based on understanding the concepts involved and, second, she might have an intuition that, say, happiness is an intrinsic good, or that no object can be in two wholly different places at the same time, based on her inability to think of counterexamples to those claims. In each case, a rational intuition, or insight, would be the evidence on which the justification rests, but the intuitions would be based on different things.
So perhaps a better way to formulate "A priori knowledge: yes or no?" than either of our answers suggested would be:
Yes: Some of our beliefs can be justified by immediate intuitions or insights independent of empirical evidence sufficient to demonstrate the inductive reliability of those intuitions/insights.
No: None of our beliefs can be justified, even provisionally, in that way. (I.e., epistemic justification is impossible, or it can only be acquired via empirical induction -- that is, via a posteriori reasoning.)
What do you think?