The Relevant Sense of “Independent”
It is also important to examine in more detail the way in which a priori justification is thought to be independent of experience.
Here again the standard characterizations are typically negative.
There are at least two ways in which a priori justification is often said not to be independent of experience.
The first begins with the observation that before one can be a priori justified in believing a given claim, one must understand that claim.
The reasoning for this is that for many a priori claims experience is required to possess the concepts necessary to understand them (Kant 1781).
Consider again the claim that if something is red all over then it is not green all over.
To understand this proposition, I must have the concepts of red and green, which in turn requires my having had prior visual experiences of these colors.
It is possible that a priori justification is fallible, but that we never, in any particular case, have reason to think it has been undermined by experience. Further, the fallibility of a priori justification is consistent with the possibility that only other instances of a priori justification can undermine or defeat it.