In this two-volume work, the author argues that the avant-garde features of Giambattista Vico's thought stem directly from his engagement with theological traditions, and his concern to develop a Catholic apologetic. This claim is established through a thorough engagement with all Vico's texts. This first volume deals with Vico's early writings, where he makes his fullest statements concerning humanist vision and Christian metaphysics. It focuses on Vico's baffling but intriguing outline of a metaphysics in the "De Antiquissima Italiorum Sapientia". Hints are given concerning the import of the metaphysics for the later writings, and the study argues that Vico's thought represents an "alternative" theological modernism, at once more radical and more orthodox than the proposals of Kant and Hegel.