In a recent paper, I place Thomas Aquinas’s denial that God is a substance in the context of a philosophic and theological tradition, focusing on the philosophic legacy he inherits. His conclusions are a development of both. In particular, he brings to light the consequences of finite being. His definition of substance is neither idiosyncratic nor trivial. It has discernible historic roots, as well as metaphysical and epistemic significance. Further, this paper shows that his conclusions are not in tension with the Christian tradition, but rather illuminate and defend the language and limits of theology.