This dissertation focuses on questions regarding the metaphysical and psychological possibility of self-deception and attempts to show that self-deception is a phenomenon best characterized as both motivated and intentional, such that self-deceivers can be held responsible for their deceptions in a stronger sense than that of being merely epistemically negligent. In Chapter One, I introduce the paradoxes of self-deception, which arise when one attempts to draw a close analogy between self- and other-deception, and I discuss the various ways in which one might characterize an unwarranted belief as irrational. I go on to show how the various ways one understands interpersonal deception may mirror the various accounts one might give of self-deception. I concluded the chapter with a brief discussion of the role of empirical studies in philosophical investigations of irrationality. In Chapter Two, I look more closely at a particular kind of intentionalist account of self-deception, namely the claim that we must suppose the existence of a partitioned mind to make sense of the so-called "internal irrationality" of the self-deceiver. I discuss both stronger and weaker versions of this theory, in an attempt to show that it tends to raise more metaphysical worries than it solves. I argue further that if there is such a thing as divisions within the mind, an account of self-deception centered around such divisions will not get the intentionalist about self-deception what he or she wants. In Chapter Three, I move on to discuss non-intentionalist accounts of self-deception. Such theories have gained in popularity in recent years, due to their appeals to explanatory parsimony. Against these theories, I argued that there are certain phenomenon we take to be central to self-deception that Mele, Barnes, et al. cannot account for. I therefore propose that a more robust account of self-deception is necessary to make sense of these phenomena. Chapter Four attempts to provide such an account. I claim that if we focus more heavily on the diachronic process by which self-deceivers elicit and/or maintain their beliefs over time, what emerges looks much more like an intentional project aimed at the manipulation of one's evidence or evidential standards than a mere more-or-less unconscious process of motivated biasing. I suggest that such a view can escape the paradoxes of self-deception, while at the same time making sense of the features lacking on non-intentionalist accounts. Finally, in Chapter Five I examine the morality of self-deception. I argue that self-deceivers are not only epistemically but also morally responsible for their self-deceptions, and that self-deception generally represents a moral failure on the part of the moral agent, regardless of the normative moral theory one adopts.