What is love, what kinds of love are there, how do these relate, and how does the Christian tradition articulate the problem of love in view of the triangulation of self, neighbour and God? In short, what is the relationship between human love (eros) and divine love (agape)? This is the problem of love at the heart of the Chrisitan tradition in which God is love (1 Jn 4.8). A historical overview shows that four models have addressed the problem of love in tradition: univocity, equivocity, analogy and metamorphosis. In the first, eros and agape collapse into one reality. According to the second, eros and agape are mutually exclusive realities. In the third model, eros and agape relate in terms of similarities and only to a limited degree. The model of metamorphosis orients desire towards an integrative and higher transformation of eros and agape. This book develops the model of metamorphosis based on a philosophical reading of "On the Song of Songs" by Bernard of Clairvaux (1090-1153).