A Thomistic metaphysics of participation in being offers an account of rationality that is more complete and coherent than that of nonreductive physicalism. It is a reasoned understanding of how an embodied intellectual subject shares in being and intellectual life. This metaphysical framework supports an understanding of rationality as a participated power, and an essential property of human nature empowering persons to know reality and make choices accordingly. Human fulfilment in truth and love is a consequence of the grounding of (...) the transcendentals of truth and goodness in being. In contrast, nonreductive physicalism reduces rationality to processes and subjective experiences and can offer no priority between human material and spiritual fulfilment. Although a Thomistic metaphysics of participation in being has been effectively absent from Anglo-American hylomorphic philosophy of mind, this paper suggests it is time to reassess the benefits it offers. (shrink)