The Bible describes a fallen world and fallen humanity, in which minds are darkened. We reject God, and suppress the truth about him. How, then, can we know him at all? In other words, what are the noetic effects of sin? During the Reformation, doctrines of total depravity and the effects of the fall on the whole person re-emerged, with consequent implications for epistemology. If minds are fallen, how can we expect to know anything accurately? The purpose of this study is to start to answer that question by looking at some of the epistemology we find emerging from the writings of John Calvin and Martin Luther.