“It would be natural to want the best theory about rationality not to be self-effacing. If the best theory was self-effacing, telling us to believe some other theory, the truth about rationality would be depressingly convoluted. It is natural to hope that the truth is simpler: that the best theory would tell us to believe itself. But can this be more than hope? Can we assume that the truth must be simpler? We cannot.”

— Derek Parfit, Reasons and Persons (1984), p. 24