Trust is central to our social lives. We know by trusting what others tell us. We act on that basis, and on the basis of trust in their promises and implicit commitments. So trust underpins both epistemic and practical cooperation and is key to philosophical debates on the conditions of its possibility. It is difficult to overstate the significance of these issues. On the practical side, discussions of cooperation address what makes society possible-of how it is that life is not a Hobbesian war of all against all. On the epistemic side, discussions of cooperation address what makes the...