The purpose of this thesis is to investigate the phenomenon of disagreement from an epistemological point of view. In other words, this thesis explores how disagreement affects the rationality of our beliefs. In particular, I have focused on disagreements with respect to religious matters. One of the arguments I put forward suggests that in some circumstances, theists and atheists should regard one another as epistemic peers with respect to the topic of their disagreement. Next, I argue that evidence can be Permissive, meaning that in some cases, the body of evidence may support two different beliefs regarding a proposition. Finally, I argue that theists and atheists can reasonably retain their beliefs in the face of their disagreement over...