Eternity of the world

The question of the eternity of the world was a concern for both ancient philosophers and the medieval theologians and philosophers of the 13th century. The question is whether the world has a beginning in time, or whether it has existed from eternity. The problem became a focus of a dispute in the 13th century, when some of the works of Aristotle, who believed in the eternity of the world, were rediscovered in the Latin West. This view conflicted with the view of the Catholic church that the world had a beginning in time. The Aristotelian view was prohibited in the Condemnations of 1210–1277.

The ancient philosopher Aristotle argued that the world must have existed from eternity in his Physics as follows. In Book I, he argues that everything that comes into existence does so from a substratum. Therefore, if the underlying matter of the universe came into existence, it would come into existence from a substratum. But the nature of matter is precisely to be the substratum from which other things arise. Consequently, the underlying matter of the universe could have come into evidence only from an already existing matter exactly like itself; to assume that the underlying matter of the universe came into existence would require assuming that an underlying matter already existed. As this assumption is self-contradictory, Aristotle argued, matter must be eternal.

In Book VIII, his argument from motion is that if an absolute beginning of motion should be assumed, the object to undergo the first motion must either

Option A is self-contradictory because an object cannot move before it comes into existence, and the act of coming into existence is itself a "movement," so that the first movement requires a movement before it, that is, the act of coming into existence. Option B is also unsatisfactory for two reasons.

He concludes that motion is necessarily eternal.

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