Under Hylemorphism, all composed beings are composed of form and matter. Accordingly, the human being is a unified substance of soul and body. Through the operations of a human being an immaterial power is manifested which demonstrates that the rational soul is immaterial and immortal. Through these elements of Thomistic metaphysics, a clear understanding of the person emerges as both in-itself and toward-others. After key metaphysical principles such as the principle of sufficient reason are defended, arguments against the thesis which claim the person is reducible to body or soul are rebuked and the Hylemorphic account is shown to stand. Leaning on the work of W. Norris Clarke, the person as body and soul is thus shown to be the frontier of being.