The opponent in either an ordinary or religious disagreement asserts you have made a mistake. To avoid mistakes we strive to have good justification for beliefs which holds us connected to them during difficult challenges, similar to how a good boat tether, pictured on this book's front cover, holds a valuable boat throughout the many stresses placed on it. The problem is that an equivalently informed and capable opponent shows a possible mistake as relevant, and this ought to reduce confidence in the justification of the religious belief. The Epistemology of Religious Disagreement develops, by looking at foundational issues in the theory of knowledge, an understanding of justification specifically designed to describe exactly why this reduction happens.