It is obvious and well-known that it is one thing for it to appear to you that p is false, and another thing for it not to appear to you that p is true. The former prima facie justifies you in believing that ~p; the latter doesn’t.
Consider, then, know-how theories of perception. Such theories explain the way in which perception yields justification in terms of having learned how to identify the (kind of) truth in question on the basis of sensory input. It’s supposed to be like riding a bike: you’ve learned how to do it, and when you display your know-how, the result in the cognitive sphere is perceptual knowledge or justification.
Then suppose you are in a position where it doesn’t appear to you that p. Translate this into your favored perceptual theory: you’re not appeared to F-ly, there is no object of the sort required as a truthmaker for the proposition p, etc.
I wonder if such a theory can preserve the claim made in the first paragraph.
Note first that there is nothing in the know-how theory that requires the skill mastery to take one from an appearance that p to a belief that p, and nothing in the story to prevent going from the lack of an appearance that p to a belief that ~p. If the know-how theory is supplemented with some content or qualitative character of experience, then it can preserve the above characterization, but it is hard to see how it can do so otherwise.
This is all a bit abstract, so think of a particular case, the one I’ve used here before: Hume’s missing shade of blue. Hume has various color experiences, and has learned how to identify colors, both positively and negatively. He knows how to recognize when an object is green and not red, purple and not yellow, and also blue but not the missing shade of blue. Never has he experienced the missing shade of blue, but he has so internalized the lessons of experience that he doesn’t infer that a particular color is not the missing shade of blue anymore. His cognitive machinery works on every color input to generate two non-inferential beliefs: first, a belief about the particular experienced color and second a belief that the object in question is not the missing shade of blue.
We should tell a different justificatory story about these two beliefs. Why? Because when Hume finally experiences the missing shade of blue, his cognitive architecture does not produce two beliefs, one that the object in question is the missing shade of blue and another that it is not. The difference, though, is not the difference between inferential and non-inferential belief. It strikes me that the only plausible answer is in terms of the content or qualitative character of the experiences themselves. But, in that case, no purely know-how account of perception can be adequate. Yes???