Requiring occurrent propositional knowledge for epistemic moves generates a vicious regress, as illustrated by Lewis Carroll's tortoise-and-Achilles puzzle.

In both the a priori case and the perceptual case, the acquisition of knowledge seems to require attention on at least some occasions, and in both of these cases that requirement seems to be a practical one. It may be that knowledge of some propositions is required if one’s experience with a gorilla is to provide one with knowledge of the gorilla’s presence (with the propositions here being of a sort that could serve as a major premise in an inference by which one’s perceptual experience was int