What ’ s the Matter with Epistemic Circularity ?

If the reliability of a source of testimony is open to question, it seems epistemically illegitimate to verify the source’s reliability by appealing to that source’s own testimony. Is this because it is illegitimate to trust a questionable source’s testimony on any matter whatsoever? Or is there a distinctive problem with appealing to the source’s testimony on the matter of that source’s own reliability? After distinguishing between two kinds of epistemically illegitimate circularity—bootstrapping and self-verification—I argue for a qualified version of the claim that there is nothing especially illegitimate about using a questionable source to evaluate its own reliability. Instead, it is illegitimate to appeal to a questionable source’s testimony on any matter whatsoever, with the matter of the source’s own reliability serving only as a special case. 1. Two Kinds of Circularity Consider Roxanne. Although the fuel gauge in her car is reliable, Roxanne neither knows nor has justification to believe that it is reliable. Aside from the gauge, Roxanne has no source of information concerning the fuel level in the tank—she cannot see into the tank, cannot remember whether she filled it recently, and so on. Nonetheless, when Roxanne sees on Day One that the gauge reads ‘full’, she believes that the tank is full. And since she believes both that the gauge reads ‘full’ and that the tank is full, Roxanne infers that the gauge’s reading is correct. Again on Day Two, Roxanne sees that the gauge reads ‘1⁄4’, believes that her tank is 1⁄4 full, and infers that the gauge’s reading is correct. After continuing in this fashion for eight additional days, at the end of Day Ten Roxanne believes that her fuel gauge has a flawless track record, and she concludes on this basis that the gauge is reliable. There is something the matter with Roxanne’s bootstrapping procedure, such that it can confer neither knowledge nor justification to believe that her fuel gauge is reliable. Put roughly, Roxanne’s procedure attempts to vindicate the reliability of her fuel gauge in a way that requires Roxanne already to trust its testimony (or ‘testimony’). In the discussion following Jonathan Vogel’s (2000) introduction of the example, it has been widely agreed that there is something the matter with such a procedure, although as we will see there is considerable room for disagreement about what that something is. Roxanne’s bootstrapping procedure is not the only way that one might evaluate a source’s reliability by trusting that source’s own testimony. There is a more direct route as well. Consider Raymond. A visitor to the Island of Knights, Knaves, and Fools, Raymond wishes to determine whether the source before him is a knight. Raymond knows that if asked a yes or no question, a knight will answer correctly, a knave will answer incorrectly, and a fool will select an answer at random. But Raymond has no evidence concerning whether the source before him is a knight, a knave, or a fool. So Raymond asks the source himself whether he is a knight. When the source responds that he is, Raymond trusts his source’s testimony, and believes that the source is a knight.