Abstract

According to Thomas Aquinas, both logic and metaphysics are characterized by the same universal scope. The consideration of metaphysics extends to everthing which is, as its subject is being insofar as it is being. And the science of logic too considers everything which is, not as it exists in reality but insofar as the whole of being falls under the consideration of reason. Because of the equivalence between the logical sphere of reason and the real sphere of being metaphysics has an affinity with logic. This similarity is mentioned by Aquinas in order to explain the legitimate use of a logical mode of reasoning within metaphysics. Metaphysics is not identical with logic, but the modus logicus, the logical mode of reasoning, is to a certain extent useful for the philosopher in his inquiry into metaphysical matters. In his Commentary on Aristotle’s Metaphysics Thomas refers frequently to this ‘modus logicus' by which Aristotle is said to proceed in his investigation into substance. However, it is not altogether clear what this method consists in and how the similarity between logic and metaphysics, on which the modus logicus is based, should be understood. In this article I want to clarify the meaning of the modus logicusin Aquinas and its revelance for metaphysics. This might help us to understand better how according to Thomas logic and metaphysics are related to one another and in what sense they are different.