Philoponus Refused to Let Air Push the Arrow

The string has gone slack

In early sixth-century Alexandria, a lecture on Aristotle could be unsettled by a single arrow.

While the arrow touched the string, its mover was easy to name. The trouble began after the string snapped back. The archer was no longer touching the arrow, yet it crossed the courtyard. Aristotle’s account gave the surrounding air a second job: after parting before the projectile, it moved around and helped carry the arrow onward.

Philoponus taught these inherited texts, but he would not rescue that answer. Air plainly made flight harder. Why should it also be the cause that sustained the flight? He proposed that the bow impressed a moving force into the arrow. The arrow carried that force; the air depleted it instead of pushing from behind.

The diagram uses modern projectile mechanics, not Philoponus’s equations. It reconstructs the instant that mattered to him: the arrow has left the string but retains forward motion while gravity bends its path downward. The air need not become an invisible hand behind it.

A turn left unfinished

Philoponus did not discover inertia. He thought the impressed force would be exhausted, and he did not turn the idea into a general mathematical law. What he changed was the place where an explanation was allowed to live.

Motion no longer had to be renewed from outside at every instant. More than eight centuries later, Buridan would widen this crack with his theory of impetus. Galileo and Newton would eventually make the state of motion itself something a body could retain.

Historical source: Stanford Encyclopedia of Philosophy: John Philoponus.