The Celestial Movers in Medieval Physics

THE CELESTIAL MOVERS IN MEDIEVAL PHYSICS IN the spring of 1271 John of Vercelli, Master General of the Order of Preachers, sent a list of forty-three questions to three ·Dominican Masters in Theology for their consideration . Independently of each other, the three theologians were to consider each question carefully and reply promptly keeping in mind the directive of the Master General: (i) Do accepted authorities, the Sancti, maintain the doctrine or opinion contained in the articles listed? (ii) Apart from the weight of authorities, does the consultor maintain the aforesaid doctrine or opinion? (iii) Apart from the consultor's personal views, could the aforesaid doctrine or opinion be tolerated without prejudice to the faith? 1 Clearly the purpose of this questionnaire was to safeguard the truths of faith, even where the question raised was one of philosophical opinion or strictly natural science. St. Thomas Aquinas had previously given his decision on most of these questions in two private communiques to the lector of Venice, Bassiano of Lodi.2 The official questionnaire of the Master General contained nothing of importance which had not already been considered by St. Thomas in his two private replies. The questions are for the most part idle curiosities and useless fantasies, as the consultors themselves realized. However, the official questionnaire was sent to three outstanding Masters in the Order, and not all the questions are without interest to the modern reader. St. Thomas' reply to the official questionnaire has always been known to Thomists, even though little studied. The reply of the second consultor, 1 St. Thomas, Responsio ad fr. Joannem Vercellensem de articulis XLII, prooem., ed. R. A. Verardo, 0. P., Opuscula Theologica (Turin: Marietti, 1954), I, p. 211. In this list the original q. 8 is missing. • Responsio ad Lectorem Venetum de articulis XXX and Responsio ad eundem de articulis XXXVI, ed. R. A. Verardo in Opuscula Theologica, pp. 193-208. 286 CELESTIAL MOVERS IN MEDIEVAL PHYSICS ~87 Robert Kilwardby, later archbishop of Canterbury, was discovered and published by Fr. M.-D. Chenu, 0. P., about thirty years ago.3 Now with the discovery and publication of the reply of the third consultor, the great St. Albert himself/ we are in a position to compare the views of the three Dominican Masters point by point. Among the relatively few interesting questions in the list of forty-three, the first five stand out as particularly important for the historian and philosopher of science. They have to do with the cause or causes of celestial motion. In the order of appearance they are as follows: I) Does God move any physical body immediately? ~) Are all things which are moved naturally, moved under the angels' ministry moving the celestial bodies? 3) Are angels the movers of celestial bodies? 4) Is it infallibly demonstrated according to anyone that angels are the movers of celestial bodies? 5) Assuming that God is not the immediate mover of those bodies, is it infallibly demonstrated that angels are the movers of celestial bodies? To the casual reader these questions, too, might appear to be useless in this age of scientific progress. Angels, it is frequently thought, have no place in a discussion of scientific questions. Some Catholic scientists, and even some Thomistic philosophers feel considerable embarassment at the mention of angels; they would rather not mention them at all, or at least not mention them as having anything to do with the real world in which we live. In medieval literature the problem of celestial movers was not created by theologians, nor did it take its origin in any point of Catholic faith, although St. Thomas was keenly • M.-D. Chenu, 0. P., "Les Reponses de s. Thomas et de Kilwardby a Ia consultation de Jean de Verceil (1271) ," in Melanges Mandonnet (Bibl. Thomiste XIII: Paris 1930), vol. I, pp. 191-222. 4 James A. Weisheipl, 0. P., "The Problemata Determinata XLIII Ascribed to Albertus Magnus (1271) ," in Mediaeval Studies, XXII (1960), 303-354. ~88 JAMES A. WEISHEIPL aware of the guiding role of faith in this matter. The problem of celestial movers was entirely a scientific one having many ramifications. But here, as in other problems of medieval science, it...