John Philoponus
John Philoponus was a late antique Alexandrian philosopher, theologian, and scientist whose critiques of Aristotelian physics — particularly his theory of impetus and his arguments against the eternity of the world — anticipated key developments in medieval and early modern science. His work represents a crucial bridge between ancient Greek thought and both Islamic and Latin medieval philosophy, influencing thinkers from Avicenna to Galileo.
Key Ideas
Key Contributions
- ● Developed the impetus theory of projectile motion, challenging Aristotelian physics and anticipating the concept of inertia
- ● Argued against Aristotle that objects of different weight fall at approximately the same speed
- ● Mounted the most systematic philosophical attack on the eternity of the world, influencing Islamic kalam cosmology
- ● Served as a crucial intellectual bridge between ancient Greek thought and medieval Islamic and Latin philosophy
Core Questions
Key Claims
- ✓ Projectile motion is caused by an impressed internal force (impetus), not by the surrounding air
- ✓ Objects of different weight fall at approximately the same speed, contrary to Aristotle
- ✓ The world is not eternal: an actual infinite series of past moments is impossible
- ✓ Aristotelian physics and cosmology require fundamental revision on empirical and theological grounds
Biography
Life
John Philoponus (meaning 'lover of toil') was born around 490 CE in Alexandria, Egypt. He studied under the Neoplatonist Ammonius Hermiae and became a prolific commentator on Aristotle. Unusually for a philosopher of his era, Philoponus was a Christian, and his theological commitments led him to challenge Aristotelian doctrines that conflicted with Christian teaching — particularly the eternity of the world.
Critique of Aristotelian Physics
Philoponus's most revolutionary contributions were his critiques of Aristotelian physics. In his commentary on Aristotle's Physics, he rejected Aristotle's theory of projectile motion (which held that the air continues to push a projectile after it leaves the thrower's hand) and proposed instead the theory of impetus — an internal force (energeia) impressed upon the projectile by the thrower that gradually dissipates. This theory anticipated the concept of inertia and influenced both Islamic physicists (Avicenna) and medieval Latin thinkers (Buridan), ultimately contributing to the Galilean revolution.
He also challenged Aristotle's claim that heavier objects fall faster, arguing on both theoretical and empirical grounds that objects of different weight fall at approximately the same speed — an argument that prefigures Galileo's famous thought experiment by a millennium.
Against the Eternity of the World
Philoponus's Against Proclus on the Eternity of the World (529 CE) and Against Aristotle on the Eternity of the World mounted a systematic philosophical attack on the Aristotelian and Neoplatonic doctrine that the world is eternal. He developed arguments based on the impossibility of an actual infinite — arguing that if the world had no beginning, an infinite number of past moments would have had to elapse, which is impossible. These arguments were transmitted to the Islamic world and profoundly influenced the kalam cosmological argument.
Philoponus died around 570 CE. His work was condemned by the Church council of 680–681 for his Tritheist theological views, which limited his direct influence in the Byzantine world but not in the Islamic and Latin traditions.
Methods
Notable Quotes
"{'text': 'If you let fall from the same height two weights of which one is many times as heavy as the other, you will see that the ratio of the times required for the motion does not depend on the ratio of the weights.', 'source': "Commentary on Aristotle's Physics", 'year': 530}"
Major Works
- Against Proclus on the Eternity of the World Book (529)
- Against Aristotle on the Eternity of the World Book (530)
- Commentary on Aristotle's Physics Book (530)
Influenced
- Thomas Aquinas · Intellectual Influence
Influenced by
- Aristotle · Intellectual Influence
Sources
- Stanford Encyclopedia of Philosophy
- Philoponus and the Rejection of Aristotelian Science (Sorabji, 1987)
- John Philoponus (Wildberg, 2007)
External Links
Translations
Discussions
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