John Buridan

Works

• c. 1340Summulae de dialectica

  Begun as a commentary on Peter of Spain’s logic textbook and rewritten into a nominalist logic of its own, from terms and supposition to demonstration and sophisms.

• c. 1350Questions on Aristotle’s Physics

  Paris lectures on the Physics in their final redaction: a thrown body moves on by an impetus given to it, which only resistance and gravity wear away.

Position

Buridan’s logic is nominalist: only individual things exist, and general terms signify individuals by way of concepts in the mind. He set out this view in the Summulae de dialectica, a textbook that began as a commentary on Peter of Spain and became an independent work, and in treatises on consequences and on sophisms. He explained the truth of sentences through the theory of supposition – what terms stand for in a given sentence – and worked on paradoxes of self-reference such as “every proposition is false”. He could read Ockham’s Summa logicae but never names him, and on several points, such as the reality of quantity and Ockham’s account of motion, he argued against Ockhamist positions. In natural philosophy he is best known for the theory of impetus. A thrown body, he argued, does not move on because the air pushes it, as Aristotle had held, but because the thrower impresses on it an impetus, proportional to its speed and its quantity of matter, which would last indefinitely if the resistance of the air and the body’s gravity did not wear it down. He applied the idea to falling bodies and suggested that God might have given the heavenly spheres an impetus at creation, so that no angels were needed to move them. Similar ideas had been put forward by Philoponus and, in Arabic, by Avicenna; how they reached Paris is unclear. In his questions on the Nicomachean Ethics he argued that the will can defer its choice until the intellect has judged more fully. The ass starving between two equal bundles of hay does not occur in his works; it was probably attached to his name later, perhaps by critics. Albert of Saxony and Marsilius of Inghen carried his teaching to the new universities of Vienna and Heidelberg, and for two centuries his Summulae were read across Central Europe. Pierre Duhem saw him as a forerunner of Galileo; most historians now consider that an overstatement, since Buridan’s physics remained Aristotelian in its framework.

Life & context

John Buridan was born around 1300 in or near Béthune in Picardy and studied in Paris, where he was a master of arts by the mid-1320s. Unlike most leading masters he never took a degree in theology and never joined a religious order; he spent some three decades as a secular cleric teaching logic and natural philosophy in the arts faculty. A papal letter of 1329 calls him a cleric of the diocese of Arras and master of arts. He was rector of the university in 1328 and again in 1340. In his second term he signed the faculty’s statute of 29 December 1340 against reading authors too literally; whether it was aimed at followers of Ockham, as older historians thought, is disputed. He is last documented in 1358, and in 1361 one of his benefices was given to someone else, so he had probably died by then. The story that he was thrown into the Seine in a sack for an affair with a queen, which François Villon put into verse, is a legend.

Further main works

• Treatise on Consequences (Tractatus de consequentiis)
• Questions on On the Heavens, On the Soul and the Metaphysics
• Questions on the Nicomachean Ethics