Avicenna and Aquinas’s De Principiis Naturae, cc. 1–3

1 Aristotle, Metaphysics 5.1.1012b34-1013a16: “We call a principle . . . (3) that from which, as an immanent part, a thing first arises, e.g. as the keel of a ship and the foundation of a house, while in animals some suppose the heart, others the brain, others some other part, to be of this nature. (4) That from which, not as an immanent part, a thing first arises, and from which the movement or the change naturally first proceeds, as a child comes from the father and the mother, and a fight from abusive language. . . . (6) That from which a thing can first be known; for this also is called the principle of the thing, e.g., the suppositions are the origins of demonstrations.” 577 The Thomist 76 (2012): 577-610 AVICENNA AND AQUINAS’S DE PRINCIPIIS NATURAE, CC. 1-3 R. E. HOUSER Centre for Thomistic Studies Houston, Texas T HE SHORT TREATISE De principiis naturae ad fratrem Sylvestrem (De principiis naturae), addressed to an otherwise unknown brother Dominican, was composed by Br. Thomas of Aquino, O.P., early in his writing career (1252-56). In the oldest catalogue of his works, its companion piece, De ente et essentia, is also addressed to his “brothers and associates” (ad fratres et socios). Both works were written for his confreres at Paris, in response to the kind of request Thomas honored throughout his life. Here, for the first time in his career, he set out systematically the “principles of nature”: matter, form, privation, agent, and end. In the Aristotelian tradition, such “principles” are conceived in two ways: as ontological principles found in real physical things and as cognitional principles which must be understood from the outset when pursuing any demonstrative science.1 Later in his commentary on the Physics, Thomas said that in book 1 Aristotle had presented the real “principles of natural things,” while in book 2 he had laid out “the principles of natural R. E. HOUSER 578 2 Aquinas, II Physic., lect. 1: “Postquam philosophus in primo libro determinavit de principiis rerum naturalium, hic determinat de principiis scientiae naturalis.” 3 Avicenna, Liber primus naturalium: Tractatus primus de causis et principiis naturalium, ed. S. Van Riet (Leiden: Brill, 1992). science.”2 The difference between the two is one of emphasis, but that emphasis will prove helpful in understanding De principiis naturae, where Thomas focuses on them as principles of natural science. As Thomas conceived it, his task in De principiis naturae was to offer a concise presentation of the principles of nature, and therefore of natural science, in order to help his confreres understand them. In order to do so, four options lay before him: he could offer his own views, without reference to particular philosophers, or he could turn to the texts of one of the three authors who represented for him the grand Aristotelian tradition of physical science: Aristotle himself or the two most important Muslim Aristotelians, Avicenna and Averroës. His way of writing philosophy within a tradition led him to eschew the first option, since he took truth where he found it and was happy to give credit to pagan and Muslim philosophers. The difficulties of Aristotle’s text (which were exacerbated in Michael Scot’s Latin translation, taken from the Arabic translation) led him to the Muslim philosophers. At the present time, the predominant interpretation of De principiis naturae is that Thomas’s primary source was Averroës, but this view is implausible. Averroës had composed a very detailed, line-by-line commentary on each of Aristotle’s books, but what Thomas’s confreres needed was a brief introduction, bringing together the main points they must learn. This was unavailable from Averroës, but could be offered by way of a suitable condensation of the Latin translation of Avicenna’s Physics of the Healing, Book 1, known to Thomas as the Liber primus naturalium: Tractatus primus de causis et principiis naturalium.3 In what follows I will offer a detailed comparison of Avicenna’s presentation of the principles of nature in that text with Thomas’s presentation in De principiis naturae. What emerges from this Quellenforschung is that Aquinas’s presentation of...