Explain how Thomas Aquinas attempts to prove the existence of God.

1 – The Argument of the Unmoved Mover - In his first argument, Aquinas tries to prove that God must be the cause of motion in the universe. Aquinas defines, using Aristotle’s dichotomy of potentiality and actuality, that some things are in motion and others the potential to be in motion. Every thing requires a mover, but since an infinite regress of movers is impossible, there must be an unmoved mover whom is the source of all motion. Aquinas states that this “unmoved mover “ is what we call God.

2 – The Argument from Efficient Causes - The second argument argues that God must have been the First Cause, or creator of the universe. Aquinas argues that some things are caused, and those which are have been caused by something else. Since, again, an infinite regress of causation is impossible, there must be an uncaused cause that is the first cause. This “causer”, Aquinas says, is what we call God. This argument is similar to the argument of the unmoved mover, however in this argument Aquinas tries to prove that God must be the First Cause or creator of the universe and not just the source of motion.

3 – The Argument from Contingency  - Aquinas’ Third Way is probably the most important argument of all, as he seeks to establish dependence of the world on God. Aquinas explains that in nature things can either exist or not exist, and if so, given infinite time, at some point everything must not be. But if there was nothing, nothing could come from it. Therefore something must necessarily exist. Everything necessary must be either caused or uncaused, yet a series of necessary things cannot go on eternally as there is no explanation for this. Thus, there must be something that has of itself its own necessity, which to Aquinas is God.

4 – The Argument from Degree - The argument from degree or “way of perfection” is more an explanation of a standard for morality. As Aquinas explains, all good things must resemble the most perfect and good thing. Yet humans are not perfect, so there must be something non-human which is a perfect being with which to resemble good, and this must be God.

5 – The Teleological Argument (from Design) - Aquinas’ final argument, the argument from design, is a teleological argument. Here he suggests that inanimate objects, such as planets, could not have ordered themselves because they lack the intelligence to do so. Yet they are aligned and in orbit, so some being with intelligence must have ordered them. Since humans are intelligent but cannot move all inanimate objects, the only other intelligent being is God.