This first volume of the smaller works of Thomas Aquinas includes the famous Compendium of Theology: the theological work Aquinas wrote at the request of his secretary, Reginald. It is basically a simplified version of the Summa Theologiae, since his secretary had requested a work on theology in less dense terms. This volume also contains the treatises On the Principles of Nature, On Being and Essence, On Separate Substances, and On Kingship.