Abstract

In Summa theologiae, Ia, 75.5, Aquinas writes, "It is evident that all that is received in anything is received in it according to the mode of the receiver." Aquinas employs this principle throughout his career and across the full range of philosophical topics. Beginning with Quaestianes de veritate 2.5, he employs a more universal formulation which he applies even to divine being: "All that is in anything is in it according to the mode of that in which it is." As modus is the term common to the principle's two formulations, I call it the modus principle. ;The dissertation is a comprehensive study of Thomas's use of the principle, based on computer research done with the Index Thomisticus and the St. Thomas CD-ROM. The 200 texts located are considered according to applications in the order of knowing, the order of being, and the order of predicating. In brief, Aquinas employs the modus principle and the term modus to give account of the intelligible coenactment in knowledge of the knower and the known; to give account of the entitative contrariety evident among beings; and to frame an analogy of being based on a primacy of existence. The principal conclusions drawn from the textual survey are that the modus principle belongs among the most basic axioms of Thomas's metaphysics, that it pertains directly to the metaphysical ultimate of his thought, namely esse, and that at the heart of the principle is a concept central to his metaphysics, namely modes of existence. ;When Aquinas subordinates formal contrariety to an actuality more ultimate than form, namely existence, a new concept of existential distinction emerges. Modus is a term of entitative contrariety that becomes necessary when a real duality of essence and existence is seen as necessary to all finite being. As Thomas traces this entitative composition to a participation in ipsum esse commune, and ultimately to a participation in ipsum esse per se subsistens, the term modus and the modus principle are seen to be in the service of his creationist metaphysics