Takes Inspiration from the Idea of Aristotles Prime Mover. Aquinas observes that everything in the world has movement, or has potential to be moved. An example is people growing old over time and dying. Therefore there must be something that causes it to move, the change has to be caused by something else as nothing moves on its own. There must be a first mover that is unchanging and unmoving, that is responsible for the motion in the universe. Aquinas calls this God.
If everything was always in motion there would be an infinite regression, this cannot be the case, because there would be no starting point to the universe, it implies that the universe never really ''began'' There must be a beginning