 Lefèvre’s mathematical examples in natural philosophy are all the more remarkable because he elsewhere disparaged the calculatores who followed in the tradition of Thomas Bradwardine (Lefèvre 1510: 2r; Rice 1972: 227). Clearly, he did not oppose the mathematical nature of the so-called Merton school’s natural philosophy, but rather certain aspects of their exposition. Lefèvre mistrusted the genre for which the calculatores were famous, the sophismata; he saw them as mere logical puzzles, sophistry rather than truth-telling examples—a prejudice perhaps inherited from Ermolao Barbaro (Dionisotti 1955). This suggests that Lefèvre thought his own use of mathematical reasoning in natural philosophy was different—that it was not sophistry, but truly depicted nature. What then were the sources of Lefèvre’s mathematical approach to natural philosophy, if not among the fourteenth-century calculatores? One possibility is the school of Albertists, who became especially powerful in fifteenth-century Paris, partly in opposition to the nominalists and calculatores whom they believed had profaned the university (Kaluza 1988). The Albertist textbook tradition of natural philosophy placed a high value on mathematics for understanding the physical world (Hoenen 1993: 328–330).