The notion of substantial conversion by Thomas Aquinas

Abstract

This article intends to investigate the idea of “substantial conversion”, presented by Thomas Aquinas, in his theory on transubstantiation in Summa Theologiae III, q.75. Here we seek to recognize the heterodox character of this conversion in relation to the others in the ordinary conceptual framework presented by Thomas, of an Aristotelian nature. As will be seen, the idea of conversion present within the Stagirite's metaphysics concerns generation and corruption, in which the notion of form is supposed. On the contrary, in the possibility of the idea of substantial conversion, there is another scenario, unexplored by the Corpus Aristotelicum, in which one substance becomes another completely, resulting in a total conversion. In this sense, we aim to present, firstly, the historical and theological context of discussions on transubstantiation. Next, we will seek to show the Aristotelian paradigm of natural conversions, assumed by Thomas in the ordinary environment of nature. Finally, it will be shown what substantial conversion consists of in more detail, based on the philosophical arguments relating to it that Aquinas makes, seeking to identify the metaphysical relevance of this possibility to philosophically situate the miraculous phenomenon that occurred in the sacrament of the Eucharist.