THE DIARY PROBLEM

In rummaging through my attic, I find an unusual diary that I have not looked at since I last wrote in it five years ago. In it is an extensive list of propositions that I then believed. As I look through the list, I see that many of the propositions are ones that I still believe, but some of the entries surprise me. I had forgotten that I ever had such opinions. The diary does not provide information about why I had these opinions or the conditions under which I formed them. All it tells me is that these were my opinions at the time. As I consider the entries, I wonder whether they have any epistemic relevance for me now. Does the fact that I believed these propositions five years ago give me a reason to alter my current opinions? If so, why? Call this “the diary problem.”

The diary problem raises the question of how, if at all, one's own past opinions should figure in deliberations about what now to believe, and does so in a way that focuses attention on the intellectual authority of one's own past self. The paradigmatic issues of intellectual authority concern other people. However, questions of authority can arise about one's past self as well, and as I discuss in Chapter 6, they can also arise about one's own future self.