Spirit's Gift is the first book in English devoted to the philosophy of Claude Bruaire (1936-1982). Its focus is the notion of gift, a notion that has recently been the subject of lively debate involving Jacques Derrida, Jean-Luc Marion, Marcel Mauss, and others. What makes Bruaire's approach to this subject distinctive is that he treats it ontologically. This book critically examines the two main insights that govern Bruaire's ontology of gift (ontodology). First, gift is being in its spiritual way of being. "Spiritual" in this case does not stand for one quality among others, but, more radically, it is what makes being be itself. Second, being itself (ipsum esse) is gift only because, as Christian Revelation suggests, the fullness proper to pure act is first of all an absolutely free donation in itself and to itself before being donation to another (creation). The coalescence of being, freedom, and spirit grounds the claim that being is gift. Bruaire's thought is presented in dialogue with his two main sources: German Idealism (Hegel and Schelling) and Christian revelation. Bruaire spent the bulk of his career as a professor at the Sorbonne in Paris. Although not himself a Hegelian, he enjoyed and enjoys great standing as a scholar of and commentator on Hegel's philosophy. With Marion, Bruaire was a founding member of the French edition of the theological journal Communio, and he was held in high regard by the great Swiss theologian Hans Urs von Balthasar. Bruaire's metaphysical account of gift also has affinities to that offered by Karol Wojytla - and subsequently developed under his pontificate as John Paul II. While Bruaire's understanding of gift is decidedly philosophical, it is also of considerable theological interest, bearing as it does upon questions of Trinitarian theology, theological anthropology, and the Catholic sacrament of marriage. Rightly understood, his conception of gift sheds considerable light on the Thomistic understanding of Ipsum esse subsistens. It can also contribute to a philosophical retrieval of the category of causality and to the elucidation of the ontological ground of ethics.