Resuming a discussion from earlier, I wanted to say more about Conee's criticism of disjunctivism. Remember that Conee criticized the disjunctivist's epistemological claim that the evidence we have in the good case is better than the evidence we have in the bad by appeal to this principle:
The Defeat Principle: X’s justification for a belief is not stronger than Y’s justification for the same belief, if their respective justifications are prone to being equally well defeated by the same defeaters.
To avoid the difficulties discussed earlier, we should read the principle as follows:
The Defeat Principle (B): X’s justification for a belief is not stronger than Y’s justification for the same belief, if their respective justifications are prone to being equally well defeated by all of the same defeaters.
There are four things for the experiential disjunctivist to say.
First, Conee's paper gives us one example of one defeater that seems to defeat the justification provided by perception and hallucination equally well. I am not confident that this defeat principle is one that the epistemological disjunctivist has to deny because I am not confident that there is not some possible defeater that will defeat the justifications subjects have for beliefs based on perception and hallucination to different degrees.
Second, the experiential disjunctivist who also opts for evidential disjunctivism thinks that (i) it is possible for there to be subjective differences between perceptual experience and hallucination when these mental states are introspectively indistinguishable and (ii) that these subjective differences confer epistemic benefits upon the subject who is fortunate enough to have had a perceptual experience rather than hallucination. If my first response is mistaken and Defeat Principle (B) does apply to the view that combines epistemological and experiential disjunctivism, that is because all of the same defeaters will apply to experience-based justifications when these experiences are introspectively indistinguishable even if there are subjective differences between the relevant experiences. Since this seems wrong, Defeat Principle (B) is false if it threatens the view that combines experiential and epistemological disjunctivism.
Suppose we have a series of experiences: e1, e2, e3, and e4. These are the experiences you would have if you looked at very similar but increasingly dark paint chips: c1, c2, c3 and c4. These chips have been set out on the table and left unattended while you scout the store for more promising shades of gray paint. Suppose e1 and e2 are indistinguishable, e2 and e3 are indistinguishable, and e3 and e4 are indistinguishable. Owing to subjective differences between e1 and e3, these experiences are distinguishable. Owing to subjective differences between e2 and e4, these experiences are distinguishable. It should be that subjectively different and introspectively distinguishable experiences justify different beliefs and be liable to defeat from different defeaters. For example, the degree to which e3 will justify believing that you are looking at c3 is greater than the degree that it justifies believing that you are looking at c1. If someone says that you are looking at c1 but you believe that you are not, the justification for this belief will be defeated by their testimony to a greater degree if you are undergoing e2 than it would if you were undergoing e3 or e4. However, if we say that all the same defeaters will apply to experience-based justifications when those experiences are indistinguishable, we get the result that all the same defeaters apply to e1 and e2 in virtue of their indistinguishability. All the same defeaters apply to e2 and 3 in virtue of their indistinguishability. All the same defeaters apply to e1 and e3 in spite of the fact that they are subjectively distinguishable because this follows from the previous two claims. And now I need to take back the claim that the justification for this belief will be defeated by their testimony to a greater degree if you are undergoing e2 than it would if you were undergoing e3 or e4. That seems daft.
Third, suppose S forms the belief that p on the basis of fallacious reasoning but then forgets the reasons for which she believed p. Suppose S’ comes to know that p is the case but then forgets the good reasons that led her to believe p. It seems that all the same defeaters would defeat the justifications they had for their beliefs to the same degree and so Defeat Principle (B) implies that their justifications are equally good. If you think that memory has a purely preservative function and agree with Owens that forgetting the bad reasons that convinced S to believe p should not lead to an improvement in the epistemic status of that subject’s belief, you can either accept Defeat Principle (B) and say that memory can never preserve the justified standing of a belief when the subject forgets her reasons for believing or reject the principle and say that in spite of their equal susceptibility to defeat, the subject who seems to know p has better justification for believing p than our first subject.
Fourth, it seems plausible that experience gives us reasons to believe. It seems plausible to say that experience gives us reasons to believe beyond those that introspection provides. Suppose I have the sort of conscious experience in which it looks to me as if p. Suppose you have a conscious experience indistinguishable from mine. I suppose that introspection and some background beliefs would give you some evidence for beliefs about the external world, but I would think that these reasons are different from the reasons provided by experience and that they are typically worse than the reasons provided by experience. However, if the gods were to tell us that our experiences are not veridical, our beliefs about the external world would presumably be defeated and defeated to the same degree. According to Defeat Principle (B), if this is true, I was either wrong to say that experience gives us reasons that introspection does not or wrong to say that they were better. I think these examples show that there is something seriously wrong with the Defeat Principle.