chapter 8 Thomas Aquinas, Roger Bacon and the Magicians on the Power of Words Steven P. Marrone Sometime in 1266 or 1267 Roger Bacon wrote his Opus maius. It was one of three works Bacon composed in those years intended for Pope Clement IV, who had written to him in 1266 inquiring about his reputedly path-breaking investiga- tions into the sciences.1 Bacon’s hope was to win over the pope for his plans to inaugurate a reform of all the fields of higher learning. In Book 4, where Bacon was advancing ideas that together constituted a small treatise on the science of astrology, he took time to lay bare his thoughts on the power of the spoken word: For since the word [verbum] is generated from the natural interior parts [of the human body] and is formed by thought and by careful oversight, and [since] man takes delight in it and it is the most proper instrument of the rational soul, therefore it has the greatest efficacy of all the things that are produced by man, especially when it is brought forth with firm intention, great desire and unflinching confidence.2 By itself, the assertion seems innocuous enough. But in fact what Bacon was doing here required a good deal of courage. For Bacon was taking a stand on what had become a controversial issue by the time of the 1260s. His defense of the power of words was part of an effort to lay down a theory explaining in terms acceptable to the natural philosopher how incantations, of a special 1 On Bacon’s chronology, see A.G. Little, “Introduction: On Roger Bacon’s Life and Works”, in: A.G. Little (ed.), Roger Bacon Essays, Oxford 1914, pp. 1–31; id., “Rogerus Bacon O.F.M.”, in: C.H. Lohr (ed.), “Medieval Latin Aristotle Commentaries. Authors: Robertus-Wilgelmus”, in: Traditio 29 (1973), pp. 115–121; and especially J.M.G. Hackett, “The Meaning of Experimental Science (scientia experimentalis) in the Philosophy of Roger Bacon”, PhD Thesis, University of Toronto 1983, pp. 40–47. 2 Roger Bacon, Opus maius IV, Treatise on Astrology, in: J.H. Bridges (ed.), The “Opus Maius” of Roger Bacon, 2 Vols. and Suppl., Oxford 1897 and London 1900, Vol. 1, p. 399. © koninklijke brill nv, leiden, 2018 | doi:10.1163/9789004379299_010 thomas aquinas, roger bacon and the magicians 217 sort, managed to produce the wondrous effects that some magicians of his day claimed they did. Bacon was thus inserting himself into the debate over the reality and the power of magic. It is not an exaggeration to say that the thirteenth century represented a golden age in western Europe for the arts of learned magic. The introduction into western literate circles in the twelfth century of a massive amount of the learning of the ancient Greek world and of medieval Arabic and Hebrew tra- ditions, which inaugurated the rise of scholastic thought and an appreciation of what were already by the end of the 1100s being called the sciences, brought with it a host of works professing themselves to be about various sorts of an erudite magic. By the thirteenth century enough of these latter compositions had been translated into Latin and circulated among Latinate scholars for there to be the beginnings of practiced magic among a western educated elite.3 One type of this magic was dependent on a resurgent astrology but identifiable in particular by the engraving or founding of images, talismans reportedly capable of working marvels, and this was already in the twelfth century referred to as a “science of images”.4 When Bacon came to write his Opus maius this science could already claim a dominant place among what Norman Cohn has taught us to regard as actually practiced forms of ritual or ceremonial magic.5 For an example of a medieval Latin text professing, among other things, a science of images, we can do no better than a work translated from Arabic into Castilian Spanish at the court of King Alfonso X in 1256 or shortly there- after and then subsequently, and probably not by many years, from Spanish into Latin.6 This is the work known to the west as Picatrix, Latin version of the original Ghāyat al-hakīm or Aim of the Sage, composed in Spain by an anony- mous Arabic author in the mid-eleventh century. Though Picatrix apparently did not circulate outside of Spain before the fifteenth century—the first author to refer to it is the Florentine Neoplatonist, Marsilio Ficino—it can stand for us as representative of a type of work familiar elsewhere in western Europe by the second half of the thirteenth century. It draws on magical traditions active in the Arabic world by the ninth century and reaching back to Sābian texts record- 3 On the introduction and rise of learned magic in the twelfth and thirteenth centuries see the comments of S.P. Marrone, A History of Science, Magic and Belief from Medieval to Early Modern Europe, London 2015, pp. 18–30 and all of Ch. 3. 4 Ibid., pp. 19–21, on early, twelfth-century, references to a “science of images”. 5 See N. Cohn, Europe’s Inner Demons.The Demonization of Christians in Medieval Christendom, rev. ed., Chicago 1993, pp. 102–111. 6 See Picatrix—The Latin Version of the Ghāyat Al-Hakīm, (ed. D. Pingree), London 1986, p. 1..