The purpose of this thesis is twofold. First, to examine what it means to Become Christian from the perspective of doctrinally based catechetical teachings, biblical foundations, and historical reception of the Roman Catholic Faith Community.s second, from a systematic theological perspective, to bring together social psychology and theology to bear on this question. We first examined recent theoretical developments in the field of social psychology in the study of the self, including the influential Tripartite Model of the Self. We then used doctrinally based catechetical teachings, biblical foundations, and historical reception to examine, from a theological perspective, what it means to become Christian. Bringing together Social Psychology and Theology, we then explored the facts, both theological and psychological, relating them to each other and articulating jointly an understanding of what it means to become Christian. We have found that when one becomes Christian, one is understood to partake in the divine nature of God, develop a familial bond with God through Christ and become part of the entire people of God. We have argued that becoming Christian is a transformation of one's identity and can be understood, through the Tripartite Model of the Self, as a transformation of the individual self, the relational self, and the collective self. We have further argued that the Kaleidoscopic Tripartite model of the Christian self gives us the tools to further understand the relationship between the different Christian selves, the controversies regarding their relationships, their transformation through key events and how they are linked to priestly, prophetic, and kingly (an. allusion to 1 Peter 2,9) behaviour.