In this article, the philosophical-anthropology of St. Thomas Aquinas is examined. In particular, the non-dualistic aspects of his anthropology are explicated and shown to have the potential to provide an underpinning for a holistic approach to psychology. In the course of this examination, parallels are drawn between Thomism and existential-phenomenology. The article concludes with an exploration of the ways in which a dialogue between existential-phenomenology and Thomism might benefit both traditions of thought, particularly as regards their relevance to metapsychology.