In this paper, we will discuss Peter van Inwagen’s contribution to the epistemological debate about revealed peer disagreement. Roughly, this debate focuses on situations in which at least two participants disagree on a certain proposition based on the same evidence. This leads to the problem of how one should react rationally when peer disagreement is revealed. Van Inwagen, as we will show, discusses four possible reactions, all of which he rejects as unsatisfying. Our proposal will be to point to hidden (...) assumptions in van Inwagen’s reasoning and ask whether he is willing to reject at least one of these to get rid of the problem. In short, our thesis amounts to the following: Of the two epistemological claims, which we call “Weak” and “Full-blown Fallibilism”, van Inwagen cannot simultaneously accept the first and reject the latter, while this is what he seems to suggest. Revealing this potential dilemma for van Inwagen’s position will lead to a more detailed discussion of how “rationality”, “truth”, “evidence” and “justification” interrelate and how a closer look at their relation might help solving the puzzle of revealed peer disagreement. (shrink)