Reflection and Disagreement


  • Adam Elga

    1. Princeton University
    Search for more papers by this author
    • *

      Thanks to Cian Dorr, Andy Egan, John Hawthorne, Agustín Rayo, David Christensen, Alan Hájek, Jim Pryor, Philip Pettit, Tom Kelly, Roger White, Sarah McGrath, the Corridor Group, and audiences at CUNY, the University of Michigan, Australian National University, the University of Sydney, the 2006 Formal Epistemology Workshop, and the 2006 Bellingham Summer Philosophy Conference.


How should you take into account the opinions of an advisor? When you completely defer to the advisor's judgment (the manner in which she responds to her evidence), then you should treat the advisor as a guru. Roughly, that means you should believe what you expect she would believe, if supplied with your extra evidence. When the advisor is your own future self, the resulting principle amounts to a version of the Reflection Principle—a version amended to handle cases of information loss.

When you count an advisor as an epistemic peer, you should give her conclusions the same weight as your own. Denying that view—call it the “equal weight view”—leads to absurdity: the absurdity that you could reasonably come to believe yourself to be an epistemic superior to an advisor simply by noting cases of disagreement with her, and taking it that she made most of the mistakes. Accepting the view seems to lead to another absurdity: that one should suspend judgment about everything that one's smart and well-informed friends disagree on, which means suspending judgment about almost everything interesting. But despite appearances, the equal weight view does not have this absurd consequence. Furthermore, the view can be generalized to handle cases involving not just epistemic peers, but also epistemic superiors and inferiors.