The book is a defense of intentionalism. According to intentionalism the phenomenal character of all mental states - such as thoughts, perceptions, emotions or bodily sensations - is determined by their intentional properties, that is by their meaning. Many philosophers of mind are attracted to intentionalism because they assume that an intentional description of mental phenomena contributes to a reduction of mental properties to physical properties. This book adopts a different point of view: We can see intentionality more fruitfully as the basis for a theory that explains how various different mental states are epistemically significant for us. Once we adopt an epistemological perspective on the mind, we can formulate an intentionalist theory that not only has more explanatory force, but is also more phenomenologically adequate than accounts available so far. The book has two parts: The first half is primarily a methodological analysis of how we should and should not study intentionality and discuss intentionalism. The second half begins the positive work of developing a successful intentionalist theory based on an enriched epistemic two-dimensional semantics for mental states.