Thomas Aquinas and the Demonstrative Character of Metaphysics

There are those who think that metaphysics is a legitimate discipline, and there are those who do not. Among those who think that metaphysics is a legitimate discipline, there are those who think that it is in the business of producing knowledge, and there are those who do not. Among those who think that metaphysics is a legitimate discipline that is in the business of producing knowledge, there are those who think that it can produce knowledge of the highest sort, and there are those who do not. The purpose of this dissertation is to show that Thomas Aquinas was among those who thought that metaphysics is a legitimate discipline that is in the business of produce knowledge of the highest sort, and that he had good reason to do so—at least by his own lights.

In the Aristotelian tradition to which Aquinas belonged, the highest sort of knowledge was demonstrative knowledge (episteme or scientia), in which the knower grasps—on the basis of universal and necessary principles—both that and why some subject necessarily has some property. Chapter 1 draws attention to the difficulties that Aquinas’s peripatetic predecessors had in giving a consistent account of metaphysics that could meet the standards of scientia. Chapter 2 provides an overview of Aquinas’s understanding of scientia with a view to articulating precisely what he thought its requirements were. Chapters 3, 4, and 5, respectively, consider Aquinas’s account of the subject-matter, the properties, and the principles that he thought were at issue in the science of metaphysics. On my revisionary interpretation of these three points, Aquinas’s vision of (and for) metaphysics is one that hangs together with remarkable consistency and meets all the demands of Aquinas’s rigorous understanding of scientia.