efficient cause

Noun

 * 1)  The being or event which physically brings about the change or motion that produces another occurrence or thing.
 * 2) * 1781, Samuel Johnson, quoting Sir Richard Blackmore in Lives of the Poets:
 * As to its efficient cause, wit owes its production to an extraordinary and peculiar temperament in the constitution of the possessor of it, in which is found a concurrence of regular and exalted ferments, and an affluence of animal spirits, refined and rectified to a great degree of purity.

Usage notes

 * One of the four kinds of causes recognized in Aristotelianism: material cause, formal cause, efficient cause, final cause.