Aristotle considers whether change had a beginning or end, or whether it has always existed. Some thinkers claimed that change began at a certain moment, while others held that it is eternal. Aristotle examines these possibilities and argues that change must always have existed and will always continue. Change presupposes things capable of causing change and things capable of being changed. If such capacities came into existence at some point, their coming into existence would itself require a prior change. Thus, any supposed first change would already depend on an earlier one.

He also argues that time cannot exist without change, because time is defined through change. Since time is generally regarded as eternal, change must also be eternal. Aristotle further argues that change cannot cease entirely. If one change ends, the process that brings about its end is itself another change. For these reasons, he concludes that change neither begins nor ends, but exists eternally.

Aristotle responds to objections against his claim that change is eternal, claiming that these are “not difficult to deal with” (190). One objection states that no single change can be eternal because every change has a beginning and an end defined by opposites.