The main argument for God is the First Cause: there must be something which originates motion, and this something must itself be unmoved, and must be eternal, substance, and actuality. The object of desire and the object of thought, Aristotle says, cause movement in this way, without themselves being in motion. So God produces motion by being loved, whereas every other cause of motion works by being itself in motion (like a billiard ball).

Bertrand Russell, History of Western Philosop…, loc. 750