Immunology has been referred to as the science of self/non-self discrimination. Who or what is the "I" of which we often speak? It has been identified with body, brain, soul, and memories. There has been a diversity of ways to characterize the self, including denying its importance and existence, and to date no satisfactory conceptualization has been achieved. This article addresses the concept of self from an immunological perspective, a perspective that offers insights into the philosophic issues associated with the concept of self and personal identity. The article proposes that the immunological and the psychological are two aspects of one and the same self, offers criteria for an adequate conceptualization of the self, and discusses the philosophical and psychological implications of the immunological views of self. It concludes that we must move away from a simplistic, exclusively inward or mentalistic conception of the self.