Aquinas's virtue-based ethics is grounded in his metaphysics, and in particular in one part of his doctrine of the transcendentals, namely, the relation of being and goodness. This metaphysics supplies for his normative ethics the sort of metaethical foundation that some contemporary virtue-centered ethics have been criticized for lacking, and it grounds an ethical naturalism of considerable philosophical sophistication. In addition, this grounding has a theological implication even more fundamental than its applications to ethics. That is because Aquinas takes God to be essentially and uniquely being itself. Consequently, on Aquinas's view, God is also essentially goodness itself. Aquinas's metaphysical grounding for his ethics is thus meant to be understood in connection with his more fundamental views regarding God's nature, and in particular his views of God's simplicity. This metaphysical grounding confers significant philosophical and theological advantages on his ethics.
