Psychological thesis: For any subject S and any proposition p: it’s not possible for S to hold a belief that p on the basis of the belief that it is in S’s best interest to believe p.
Weak rationality thesis: For any S and any p: it’s not possible for S’s belief that p to be epistemically rationalized by S’s belief that it is in S’s best interest to believe p.
Strong rationality thesis: For any S and any p: it’s not possible for S’s belief that p to be all things considered rationalized by S’s belief that it is in S’s best interest to believe p.
(Kelly doesn’t clearly distinguish between the weak and the strong rationality theses; however, it’s pretty clear that he’s committed to both.)
Here’s a counterexample to all three theses:
A semi-evil demon hands Sheila a folded sheet of paper. Before she unfolds the sheet, the demon tells her the following: “On this paper I have written a single sentence. If, upon reading the sentence written on this piece paper, you come to believe the sentence is true, I will give you a million dollars. If not, I will inflict severe bodily harm upon you.”
Suppose furthermore that Sheila has strong evidence that the demon is i) a reliable mind reader, ii) capable of carrying out his promise, iii) sincere in his promise. Sheila thus comes to believe the following proposition:
P: It is in my best interest to believe that the sentence written on the sheet of paper is true.
Next, Sheila opens the sheet of paper and reads the following sentence:
S: It is in your best interest to believe this sentence is true.
Sheila reason as follows: the written expression, “this sentence” refers to the sentence written on the sheet of paper. By P, Sheila concludes that it is in her best interest to believe said sentence. Since the sentence simply says that it is in her best interest to believe said sentence, Sheila concludes:
C: The sentence written on the sheet of paper is true.
Reflecting on this case, I think the following three claims are plausible:
1) Sheila believes C on the basis of her belief that P.
2) Sheila’s belief that P epistemically rationalizes her belief that C.
3) Sheila’s belief that P all things considered rationalizes her belief that C.
Clearly, 1) is inconsistent with Kelly’s psychological thesis; 2) is inconsistent with the weak rationality thesis; and 3) is inconsistent with the strong rationality thesis.