My research focuses on the philosophy of imagination. Within the analytic tradition, there recently has been a growing interest in imagination. The current research lies at the crossroads of various sub-disciplines of philosophy, including aesthetics, moral psychology, ethics, epistemology, and philosophy of mind. My work joins this choir as a voice from within philosophy of mind. My dissertation addresses two questions within philosophy of imagination. What I call the Relation Question asks what is the proper relation between supposition and imagination, and what I call the Unification Question asks what is the imagination. With regards to the Relation Question, philosophers answer it in one of two ways: either supposition and imagination are distinct mental capacities (what I call two-nature views) or supposition is a kind of imagination (what I call one-nature views). I argue that both views fail to explain all of the features central to the relation. With regards to the Unification Question, many philosophers doubt it has an answer because there is no clear way to unify the disparate activities of imagination. I argue that this skepticism is the result of mischaracterizing the relation between imagining and supposing. Thus, I answer both the Relation and Unification Questions by arguing that both imagining and supposing (as we typically understand these terms) are both instances of what I call the as-if-true attitude. I call this the as-if-true attitude view of imagining. The explanatory payoff of this is that my view can explain all of the features central to the relation without positing two distinct mental capacities (as two-nature views do) and without getting facts about supposition wrong (as one-nature views do). It also gives us a way of seeing how we might unify the different activities of imagination. Finally, I demonstrate that my view has application to what is known in the literature as the phenomenon of imaginative resistance. This phenomenon has to do with competent imaginers failing to comply with invitations to imagine certain propositions. It has been noted in the literature that there is variation to this phenomenon, where some people experience it and some do not. Some philosophers attempt to explain this by appealing to contextual factors. Thus, I call them Contextual Variant Views. I argue that these views fail to account for all of variation. I show that from my as-if-true attitude view comes another view that I call Constraint Variant View. I argue that this view can account for all of the variation of imaginative resistance.