Jean Buridan

Jean Buridan (/ˈbjʊərɪdən/;^[1]French:[byʁidɑ̃]; Latin: Johannes Buridanus; c.1301 – c.1359/62) was an influential 14th‑century French scholastic philosopher.

Buridan taught in the faculty of arts at the University of Paris for his entire career and focused in particular on logic and on the works of Aristotle. Buridan sowed the seeds of the Copernican Revolution in Europe.^[2] He developed the concept of impetus, the first step toward the modern concept of inertia and an important development in the history of medieval science. His name is most familiar through the thought experiment known as Buridan's ass, but the thought experiment does not appear in his extant writings.^[3]

The concept of inertia was alien to the physics of Aristotle. Aristotle, and his peripatetic followers held that a body was maintained in motion only by the action of a continuous external force. Thus, in the Aristotelian view, a projectile moving through the air would owe its continuing motion to eddies or vibrations in the surrounding medium, a phenomenon known as antiperistasis. In the absence of a proximate force, the body would come to rest almost immediately.

Buridan developed a theory of impetus by which the mover imparts to the moved a power, proportional to the speed and mass, which keeps it moving. In addition, he correctly theorized that resistance of the air progressively reduces the impetus and that weight can add or detract from speed.^[13] Buridan was the first to name this motion-maintaining property impetus but the theory itself probably did not originate with him. A less sophisticated notion of impressed forced can be found in the commentary of John Philoponus on Aristoteilan physics.^[14] In this he was possibly influenced by John Philoponus who was developing the Stoic notion of hormé (impulse).^[14][15] The major difference between Buridan's theory and that of his predecessor is that he rejected the view that the impetus dissipated spontaneously, instead asserting that a body would be arrested by the forces of air resistance and gravity which might be opposing its impetus. Buridan further held that the impetus of a body increased with the speed with which it was set in motion, and with its quantity of matter. This is closely related to the modern concept of momentum. Buridan saw impetus as causing the motion of the object:

...after leaving the arm of the thrower, the projectile would be moved by an impetus given to it by the thrower and would continue to be moved as long as the impetus remained stronger than the resistance, and would be of infinite duration were it not diminished and corrupted by a contrary force resisting it or by something inclining it to a contrary motion (Questions on Aristotle's Metaphysics XII.9: 73ra).^[16]

Buridan also contended that impetus is a variable quality whose force is determined by the speed and quantity of the matter in the subject. In this way, the acceleration of a falling body could be understood in terms of its gradual accumulation of units of impetus.^[14]

• Hughes, G. E. (1983). John Buridan on Self-Reference: Chapter Eight of Buridan's Sophismata. An edition and translation with an introduction, and philosophical commentary. Cambridge/London/New York: Cambridge University Press, ISBN 0-521-28864-9.
• King, Peter (1986). John Buridan's Logic: The Treatise on Supposition; The Treatise on Consequences. Translation from the Latin with a Philosophical Introduction, Dordrecht: Reidel.
• Zupko, John Alexander, ed. and tr. (1990). John Buridan's Philosophy of Mind: An Edition and Translation of Book III of His Questions on Aristotle's De Anima (Third Redaction), with Commentary and Critical and Interpretative Essays. Doctoral dissertation, Cornell University.
• Klima, Gyula, tr. (2002). John Buridan: 'Summulae de Dialectica'. Yale Library of Medieval Philosophy. New Haven, Conn./London: Yale University Press.
• John Buridan (2015). Treatise on Consequences, translated, with an Introduction by Stephen Read. New York: Fordham University Press.
• Klima, G., Sobol, P. G., Hartman, P., & Zupko, J. (2023, May 31). John Buridan’s Questions on Aristotle’s de Anima – Iohannis Buridani Quaestiones in Aristotelis de Anima (Vol. 9). Springer.

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• Klima, Gyula (2009). John Buridan. New York: Oxford University Press.
• Landi, Marcello (2008). "Un contributo allo studio della scienza nel Medio Evo. Il trattato Il cielo e il mondo di Giovanni Buridano e un confronto con alcune posizioni di Tommaso d'Aquino" [A contribution to the study of science in the Middle Ages. The sky and the world of Jean Buridan and a comparison with some positions of St. Thomas Aquinas]. Divus Thomas. 110 (2): 151–185.
• Thijssen, J. M. M. H., and Jack Zupko (ed.) (2002). The Metaphysics and Natural Philosophy of John Buridan Leiden: Brill.

• Zupko, Jack. "John Buridan". In Zalta, Edward N. (ed.). Stanford Encyclopedia of Philosophy. ISSN 1095-5054. OCLC 429049174.
• Bibliography by Fabienne Pironet (up to 2001)
• Buridan's Logic and Metaphysics: an annotated bibliography (updates the bibliography of Fabienne Pironet to 2014)
• Buridan's Logical Works. I. An Overview of the Summulae de dialectica a detailed summary of the nine treatises of the Summulae de dialectica
• Buridan's Logical Works. II. The Treatise on Consequences and other writings a summary of the other logical writings
• Buridan: Editions, Translations and Studies on the Manuscript Tradition Complete bibliography of the logical and metaphysical works