John Philoponus

John Philoponus was a Christian philosopher who dealt with logic, philosophy, physics and theology.

In his youth he studied under the Neo-Platonist Ammonius, a pupil of Proclus. He became a great critic of Aristotle through his ideas on the eternity of the universe. He criticized this argument using, for example, the doctrine of motion. He replaced the idea itself with his own theory that a body set in motion contains a certain amount of energy, so that it continues to move even when the force ceases. This body keeps moving until this energy is exhausted. This became one of the forerunners of the theory of inertia.

In his later years, he devoted himself mainly to theological questions, defending the doctrine of Creation from nothing. He also wrote several writings on the Trinity and Christology. When Church doctrine became established, Philoponus's teachings were labeled heretical, and thus his further influence was greatly curtailed.

The teachings of John Philoponus were followed by the Parisian teachers Jean Buridan and Nicolas Oresme. His printed writings continued to appear in the 15th century, and these eventually influenced Pico della Mirandola and Galileo Galilei.