Higher-order evidence is evidence about what you should think. It's nontrivial just if it allows higher-order uncertainty—uncertainty about what you should think. Mundane cases abound. I'm very confident the plane is safe, but I wonder whether I should be more (less) so—statistics is hard, after all. Theoretically interesting cases do too. Disagreement: I thought Kim was the best candidate, but my colleagues thought otherwise—I'm probably more confident than I should be. Impairment: The answer to question 17 seems obvious, but I'm running on 5 hours of sleep—I'm probably missing something. Tendencies: My argument seems convincing, but I always think my arguments are convincing—I might be overconfident. And so on.
The Question: How should evidence about what you should think affect what you should think?
Part One ("Building Bridges") sets the stage. I argue that higher-order evidence is nontrivial and important—undergirding epistemic practices like focusing, checking our work, combatting bias, and working together. But our current theories don't do it justice: those that posit connections between first- and higher-order attitudes are beset with triviality results; those that deny them are beset with paradox. All of these problems can be seen only once we use models of probabilistic epistemic logic to investigate higher-order evidence. The way forward, then, is to apply them systematically in developing our theories.
Part Two ("Evidence: A Guide for the Uncertain") does so. I argue that if you should take peer disagreement seriously, then evidence must have two features. (1) It must sometimes warrant higher-order uncertainty. (2) But it must always warrant being disposed to treat facts about your evidence as a guide. As argued in Part One, no known theory of evidence does so. I propose such a theory, encapsulated in a new deference principle---Trust---that requires you to think it likely that what the evidence supports is true. Trust allows modesty but ensures many guiding features. In fact, I claim that Trust is the goldilocks principle---for it is necessary and sufficient to vindicate the claim that you should expect free evidence to be valuable (Good 1967). Upshot: Trust lays the foundations for a theory of disagreement and, more generally, an epistemology that permits self-doubt---a modest epistemology.
Part Three will explore applications and consequences of Trust in an interpersonal setting. How should multiple agents—each satisfying Trust—react when they discover the opinions of their peers? To what extent (and in what circumstances) should disagreement lead them to moderate those opinions? To what extent (and in what circumstances) should agreement lead them to strengthen their opinions? Etc.
Can the Knowledge Norm Co-Opt the Opt-Out? (2014). Thought: A Journal of Philosophy (3) 4: 273-282. [Official Version]