Homo Abyssus is one of the most significant works of Catholic philosophy in the twentieth century. In this speculative appropriation of Aquinas, Ferdinand Ulrich lays out a vision of being as an image of divine goodness, drawing out as-yet-undiscovered treasures from Aquinas’s texts through a fundamental engagement with modern philosophy, above all Hegel and Heidegger. One of the most unique features of this vision is, as Hans Urs von Balthasar observed, “It stands face-to-face with the innermost mysteries of Christian revelation, and opens them up, without ever departing from the strictly philosophical sphere. In this respect, it overcomes the baleful dualism between philosophy and theology perhaps more successfully than any previous attempt.” The first part of the book offers a fundamental metaphysics, expounding in detail the basic structure of being in the light of creation ex nihilo interpreted as an act of radical generosity. This discussion presents novel insights into