Let's say that epistemological disjunctivism is the view that in case 1 you'll have more evidence/reasons than in case 2 for your perceptual beliefs:
C1: It looks to S as if p and that's because S's experience is veridical.
C2: It looks to S as if p and that's because S is hallucinating.
I think that in C1, p is part of S's evidence as a result of S's experience but I don't think that p is part of S's evidence in C2. Various objections have been raised against epistemological disjunctivism, here I want to discuss Conee's objections from, "Disjunctivism and Anti-Skepticism".
Conee has argued that nothing, not even the factive mental states that McDowell thinks we are in when we perceive p to be the case, could confer upon us the sorts of epistemic benefits by which we have better evidence or reasons than we have in the bad case. First, he says that a subject who perceives p to be the case and believes p to be the case is not more reasonable than a subject who undergoes a subjectively indistinguishable hallucination and ends up believing the same thing.
That seems reasonable enough, but it also seems irrelevant. McDowell will say that factive reasons give us better reasons to believe than hallucinations will and it is controversial whether it is right to say that two subjects are equally reasonable in believing what they do only if their reasons are equally good. It seems that someone can be no less than perfectly reasonable in acting wrongly, provided that their conduct can be excused. If the point of offering an excuse is to uphold
someone’s rationality or character in spite of the fact that they acted against an undefeated reason and we succeed in excusing their conduct by showing that they are just as reasonable or responsible as someone who, say, acts rightly, then intuitions about what is reasonable are not a good way to test claims about the comparative strength or goodness of reasons.
Conee recognizes that some will distinguish between judgments of reasonableness and claims about reasons, so he offers this second criticism.
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.
He observes that if some subject perceived a table and another subject had a hallucinatory experience indistinguishable from this first subject’s experience, the justification these subjects had for believing that there was a table before them would be defeated to an equal degree if told by a trustworthy person that they were hallucinating. He concludes:
"The assumption that the table and its rectangularity are directly manifested by the perception, and not by the hallucination, does not affect the capacity of the testimony to defeat. As this testimony example also illustrates, some defeaters of the
justification would have true content in the hallucination case, and untrue content in the perception case. But this difference also does not affect their capacity to defeat the respective justifications. Thus, The Defeat Principle provides another way to see that the disjunctivist assumption of perceptual directness implies no justificatory advantage."
While I agree that the testimony could defeat the justification these subjects have, I don’t think this tells us much about the justification provided by veridical experience and the justification provided by hallucination.
Suppose my justification for borrowing the neighbor’s car without permission is to drive someone to the hospital because they are in need of immediate medical attention. Your reason for borrowing your neighbor’s car without permission is to drive someone to a restaurant because they are in need of immediate romantic attention. If we are then both commanded by the
gods to return our cars, our justifications are both equally defeated but it seems that mine is better than yours.
Of course, this is about reasons for action, but we can come up with examples of reasons for belief that show that the Defeat Principle is unsound. Suppose God told me that my crystal ball will tell me who will win the derby correctly 99 times out of 100 and God tells you that your crystal ball will tell you who will win the derby correctly 87 times out of 100. My ball says that Sad Clown will win. Your ball says Bride of the Fox will win. The paper reports that Butternut Squash won the race. Before we read the paper, my justification was better than yours. I think after we read the paper our justifications are equally defeated.
We should consider one last example. 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 the Defeat Principle, 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.