In Ancient Greece, written in gold over the temple portal at Delphi was the inscription, “Know Thyself.” In the quest to know oneself, the question naturally arises: by which methods are we to come to know ourselves? The empirical methods of scientific enquiry seem to reveal much about the “outer man;” but how are we to arrive at sound and sure knowledge of what Augustine called the “inner man?” Since interior, subjective states seem restricted to first-person access alone, it might seem that introspection is the proper method by which we come to know such states, and thus, to know ourselves. However, I will argue that introspection alone will prove insufficient as a method of comprehensive self-knowledge, because it does not shed light on the aspects of mental life encapsulated by the term “unconscious.” “Gazing inward” can tell us much about ourselves but not everything, since it cannot access that which is in us, yet which lies outside of conscious awareness. To gain deeper self-knowledge, we will need to better understand our unconscious mental life. I will begin by exploring the concept of the unconscious and tracing its historical and philosophical development from Ancient Greece, through Scholastic philosophy and theology, and on into modern philosophy and psychoanalysis. Following this, I will briefly examine contributions to the study of the unconscious from contemporary psychology and neurobiology. This will lead to an exploration of the role of the unconscious in man’s spiritual and religious life, including its role in religious conversion. I will argue that we possess an unconscious awareness of a personal God, which leads to an implicit or explicit search for God. I will conclude by contrasting Freud’s view of the unconscious with the view of man’s unconscious depths offered by Augustine. This will brings the discussion full circle, back to the theme of self-knowledge. This, I will argue, can ultimately be attained only through a relationship with the God who transcends us—the God who is, in Augustine’s words, “more inward to me than I am to myself, yet infinitely above me.”