I’ve been thinking more about nihilism.
Consider a schematic case in which your total evidence is E and you are trying to determine whether you should believe P, believe not-P, or suspend judgment. Uniqueness is the view that exactly one of these choices would be rational. Permissivism is the view that more than one of these choices would be rational. Nihilism is the view that none of these options is rational.1
That’s how I posed it in an earlier post, anyway. Then I stumbled across a forthcoming article by Elizabeth Jackson & Margaret Greta Turnbull. Nodding to Feldman, they define Uniqueness as “the thesis that there is at most one rational doxastic attitude toward a proposition.” In my terms, this is the disjunction of Uniqueness and Nihilism. Ugh.
Although Feldman does say something like that, he takes it back without comment. Here’s what he says:
[The Uniqueness Thesis] is the idea that a body of evidence justifies at most one proposition out of a competing set of propositions (e.g., one theory out of a bunch of exclusive alternatives) and that it justifies at most one attitude toward any particular proposition. As I think of things, our options with respect to any proposition are believing, disbelieving, and suspending judgment. The Uniqueness Thesis says that, given a body of evidence, one of these attitudes is the rationally justified one.
If The Uniqueness Thesis is correct… evidence uniquely determines one correct attitude, whether it be belief, disbelief, or suspension of judgment.
So, I think, it’s best to see Feldman as hewing to Uniqueness in my sense.
Nevertheless, would champions of Uniqueness do better to take Jackson&Turnbull’s formulation and defend Uniqueness-or-Nihilism?
No, they would not. Here’s why.
Roger White argues against Permissivism with a host of arguments. They turn on the considering the situation in which you believe something. If Permissivism held for this case, you could change your belief and be just as rational. This wouldn’t be because you’d notice some consequence of the evidence that you had missed before, but it would just be a capricious change.
White poses this in terms of taking pills that make you change your belief: It would be no more or less rational in such a Permissive case for you to take a pill that makes you believe something different as it would be to arrive at that belief by consideration of the evidence.
Or think of a kind of Jekyll and Hyde case. Suppose a broadly Permissive case where your evidence makes it equally rational to believe P as to believe not-P. On Monday, you believe P. You go to bed, wake up on Tuesday, and believe not-P. Wednesday, you believe P. Thursday, not-P. And so on.
What’s supposed to be absurd about Permissivism is the indifference it posits between different possible belief states: You’ve done the best you could rationality-wise, but you’d be on the same footing if you kept your current belief as if you changed it. It is absurd for rationality to be this fragile, for rational belief to be this fickle (or so the argument goes). So these considerations are supposed to show that Permissivism is absurd.
The same worry applies to Nihilism just as much as to Permissivism. You can choose any option and it won’t change your score in the rationality game. The different is just that Nihilism says your score is zero.