This book is an introduction to three questions on love according to St. Thomas Aquinas (Summa Theologiae I-II, qq. 26-28). These three questions reflect on the nature of love (q. 26), the causes of love (q. 27), and the effects of love (q. 28). It is thus an introduction to the entire phenomenon of love, both as a bodily passion and an act of the will. The purpose is to present the Thomistic and broadly scholastic account of human and divine love from a philosophical and theological perspective. It aims to be a theological and philosophical study of the topic, useful both for a graduate/professional audience, as part of an undergraduate or graduate course, and perhaps for the educated reader. The thesis of the book is that, contrary to contemporary conceptions, not all loves are created equal. Some loves perfect us and some loves corrupt us. The worth of a love depends on its object and end. St. Thomas thus presents an objective and teleological account of human and divine love that is of philosophical and theological interest. The method is broadly exegetical, presenting a careful reading of the text and supplying the philosophical and theological background which the text of Aquinas assumes. The scope of the work is limited to three questions (ST I-II, qq. 26-28). References to interpretative disputes of Aquinas and references to further resources in the secondary literature will be mostly limited to the footnotes, making the body of the text accessible to more readers.