This article leads the reader to appreciate some of the importance of philosophical epistemology, to the field of theology, by way of two fascinating philosophical topics. As it does so, it provides some development and clarification of two notions important in epistemology: first, rationality, and second, the distinction sometimes called the “propositional–experiential” distinction. The first is the more central to mainstream philosophy today. Since at least Plato, philosophers have asked: what is it to know something, or to be rational or right-headed, as opposed to kooky or gullible, in believing something? Christian philosophers have applied this study to the question: can faith be known/rational/right-headed? This topic is especially germane today, with the “New Atheism” claiming that faith on the basis of Revelation is gullible or worse. The other big epistemological topic I’ll address has a history just as old. It’s discussed here and there, piecemeal, rather than systematically, today and throughout the philosophical tradition. Augustine, for one, reflects powerfully upon it. That topic is, broadly, the difference between experiential knowledge and propositional knowledge. Sometimes we seem to know something, as thoroughly as you please—you’d pass an exam on it with flying colors—without really knowing it--in a more felt, experienced, deeper way. The importance of this issue comes out in a variety of contexts. Here’s one important connection: What sort of knowledge does it take to trust God? What sort of knowledge are we missing, if we know in our minds that we should trust God, but we don’t “feel it in our nerves” (as C.S. Lewis would put it)? Experiential knowledge seems to be saliently responsible in a way that propositional knowledge isn’t, for moving us to action, affection, value judgment, and prioritizing in life (= wisdom, a gift of the HS), as well. There are further applications to judging moral responsibility, and to effective preaching and teaching