Circa 1295 - Circa 1358
Contributions to Science. Probably the most distinguished and influential teacher at the University of Paris during the first half of the fourteenth century, Jean Buridan did little experimental science himself but helped to lay the groundwork for the modern conception of science based on experimentation and observation rather than on “final” causes (that is, the how rather than the why of phenomena). He did important work in logic, reorganizing the Summary of Logic of the thirteenth-century scholar Peter of Spain, and he helped to develop the tradition of Nominalism in the philosophy of language. For the Nominalist individual beings and things alone are real. Ideas and Universals are just names. They are not real entities in nature.
Education and Career. After studying philosophy at the University of Paris, Buridan began teaching there and served as university rector. Before Buridan, most scholars taught for only two years before going on to other careers; Buridan broke with tradition and became the first scholar to pursue a university career in the arts. Like many of his contemporaries, Buridan spent most of his career explaining and extending Aristotelian works of logic, grammar, mathematics (physics), and astronomy. His preferred method was to ask a series of Questiones about particular points in Aristotle, present various interpretations and answers, and then pass judgment on these views. In this way he preserved and extended the Aristotelian corpus and other thinkers’ ideas as well. During his career Buridan wrote Questiones on Aristotle’s Physics, On Heaven and Earth, and several of his nonscientific works.
Legitimizing Science. Buridan was important for making science (natural philosophy) a legitimate study within the university and for effectively and successfully defining scientific investigation in such a way that it prevented the domination of science by theology. He taught that the behavior of the natural world should be described by a series of observational generalizations (inductive reasoning), rather than from metaphysical (that is, theological) presuppositions (deductive reasoning). Consequently, he argued that supernatural causes should not be admitted as scientific explanations of natural events—though they could, of course, explain miraculous events.
Motion. Buridan’s most important specific contribution to medieval science was an inversion of the accepted understanding of motion. Aristotle had proposed that “anything that is moved, is moved by something,” thus implying that any projectile could only move as long as another force was pushing it. Buridan suggested instead that a projectile contains a quantity of motive force within itself that has been given to it by the force that initially propelled it. This idea was not new, but Buridan went one step further and proposed that the force does not drain away on its own, but only if there is another, opposing, outside force. He therefore laid the groundwork for the idea perfected by Sir Isaac Newton in the seventeenth century: “Objects in motion tend to remain in motion unless acted upon by an outside force.” Buridan also raised questions about whether the earth stood still under rotating heavens or rotated under fixed heavens. He realized that either explanation would produce the same observed effects, but that the idea of a rotating earth was preferable because it put fewer things in motion (one earth versus thousands of stars).
Ernest A. Moody, “Jean Buridan,” in Dictionary of Scientific Biography, edited by Charles Coulston Gillispie (New York: Scribner, 1970–1980), II: 603–608.
J. M. M. H. Thijssen and Jack Zupko, The Metaphysics and Natural Philosophy of John Buridan (Leiden &. Boston: E. J. Brill, 2001).