A priori knowledge of contingent propositions
In his article Contingent A Priori Knowledge, John Turri argues that you can have a priori knowledge of propositions that neither are nor appear necessarily true. But before making this argument he argues against a proposition that Saul Kripke judges to be a priori true yet contingent.
Here is a quote from Turri:
“Kripke suggested that you could know a priori that a particular stick s is one meter long at a certain time t, despite the fact that it is obviously only contingently true that s is one meter long at t. You could know this a priori if you were, at that very time, using s to fix the reference of the term ‘meter’.”
Here is another quote from Turri, regarding why this example is a bad one:
“You could of course know that s is one meter long at time t, by virtue of knowing (a) that any stick used to fix the reference of a unit of measurement will measure exactly one such unit at the instance the reference is fixed, and (b) that s is being used at t to fix the reference of ‘meter’. But knowledge of (b) depends essentially on sense experience, so it is obviously not a priori. Consequently, the knowledge that s is one meter long at t is not a priori either.”
Turri’s example relies on the premise that if you have a non-accidentally justified belief that P, then you know that P.
Here is his example (I have slightly adapted the text).
“Sam considers whether the most unlikely possible event is not presently occurring. By ‘the most unlikely possible event’, Sam intends to designate whatever was, at the immediately preceding instant, t – 1, the possible event most unlikely to occur at the next instant, t, which is the moment at which her deliberation occurs. Sam understands the proposition in question. Solely in virtue of that understanding, it seems to her that the proposition is true, though not necessarily so. On the basis of this impression, she believes that the most unlikely possible event is not presently occurring. Her belief is true.”
This example, Turri notes, relies on a proposition that is overwhelmingly likely to be true as a matter of conceptual necessity. But it is not necessarily true. The most unlikely possible event could presently be occurring.
Turri, J. 2011. Contingent A Priori Knowledge. Philosophy and Phenomenological Research 83: 327-344.