According to Thomas Aquinas, the question about the relation between faith (fides) and religion (religio) is a question about the relation between content of revelation (beliefs) and external religious practice. In addressing this question, Thomas partly demonstrates his dependence on the legacy of his predecessors (Lactantius, Augustine, Pseudo-Dionysius), and partly shows considerable originality, connected mainly to the new ideas he has introduced into Catholic theology. Translation of articles from ‘Summa Theologiae’ and ‘In Boethium De Trinitate’ published here demonstrates, among other things, the impact that reception of new translations of Aristotle had on the Catholic ethics.