St. Thomas, Physics, and the Principle of Metaphysics

The Thomist 61 (1997): 549-66 ST. THOMAS, PHYSICS, AND THE PRINCIPLE OF METAPHYSICS LAWRENCE DEWAN, 0.P. College Dominicain Ottawa, Ontario, Canada 0 NE TWENTIETH-CENTURY school of interpretation of St. Thomas's philosophical doctrines, the "River Forest" School, holds that physics precedes metaphysics, not merely in the order of learning, but also as providing for metaphysics its proper subject of study, being as being.1 This it does by proving the existence of immaterial reality. I propose to show here that Thomas's commentaries on Aristotle, as well as his explicit description of intellectual development, run counter to this interpretation. The late Fr. James Weisheipl, surely representative of the School, in a paper published in 19762 aimed to show the need for Aristotelian physics, also called "natural philosophy," and to show that it has a congeniality with modern mathematical physics. He wished to distinguish it from both mathematical science and metaphysics. Such a natural philosophy is not only valid but even necessary for the philosophical understanding of nature itself. That is to say, there are realities 1 On the School, cf. Benedict M. Ashley, O.P., "The River Forest School and the Philosophy of Nature Today," in R. James Long, ed., Philosophy and the God ofAbraham (Toronto: Pontifical Institute of Medieval Studies, 1991), 1-16. 2 James Weisheipl, O.P., "Medieval Natural Philosophy and Modern Science," in Nature andMotion in the Middle Ages, ed. William E. Carroll (Washington, D.C.: The Catholic University of America Press, 1985), 261-76; originally published inManuscripta 20 (1976): 181-96, under the title "The Relationship of Medieval Natural Philosophy to Modern Science: The Contribution of Thomas Aquinas to its Understanding." References are to the Carroll edition. 549 550 LAWRENCE DEWAN, O.P. in nature that are not accounted for by physicomathematical abstraction, realities such as motion, time, causality, chance, substance, and change itself. The physicist needs mechanical causes, such as matter and force, but the nature ofcausality as such is beyond mathematics, where even final causality is out of place. Concepts such as potency and act, matter and form, substance and accident, quite useless to the modern physicist, are established in a realistic natural philosophy. The aforementioned concepts are not established in metaphysics, and in this connection it is important to stress the differences between metaphysics and natural philosophy and to indicate the nature and relationship of each. (273, emphasis added) Weisheipl says that metaphysics has been overloaded "with innumerable problems and areas of concern that rightly belong to the natural philosopher,"3 and he continues, "This is a perversion of metaphysics as understood by St. Thomas" [273]. A very strong condemnation, but one which is justified if the charges are true. But are they? What sort of case does Weisheipl make in the essay under consideration? He says there are at least two reasons why metaphysics presupposes natural philosophy. The first is that the latter proves the existence ofsome non-material being, and thus establishes the subject matter of a new science, namely the science of being as such. I will return to this later. The second reason is as follows: 3 One cannot help but be struck by the difference between Fr. Weisheipl's angle on things here, and that of Thomas Aquinas in, for example, II Pbys., lect. 5 (ed. Maggiolo; Rome andTurin: Marietti, 1954: no. 176): to consider concerning causes as such is tyroper to the first philosopher [i.e. the metaphysician]: for cause, inasmuch as [it is] cause, does not depend on matter as regards being, for in those also which are separated from matter one finds the intelligible aspect: cause. But consideration of causes is taken on by the natural philosopher because of some necessity: nor nevertheless is it taken on by him to consider concerning causes save according as they are causes of natural changes. [Emphasis added] Of course, one1lees well the abstract nature of the notion of cause by considering it as applicable to the separate entities; however, as I will show, only because such notions are abstract from the start can one raise the question of separate entity. ST. THOMAS, PHYSICS, AND METAPHYSICS 551 This is demanded by the nature of analogous concepts...