Thomas Aquinas's Five Arguments For The Existence Of God

Thomas Aquinas uses five proofs to argue for God’s existence. A few follow the same basic logic: without a cause, there can be no effect. He calls the cause God and believes the effect is the world’s existence. The last two discuss what necessarily exists in the world, which we do not already know. These things he also calls God.
Aquinas’ first proof says anything currently in motion was put in motion by another thing. This “mover,” as he calls it, cannot also be the “moved.” The mover transfers its own actuality of motion into the moved, which until then only has the potentiality of motion. Since nothing can have both actuality and potentiality at the same time, the mover and moved cannot be the same thing. Since the universe is motion, it could not have been something from the universe which put it into motion. Therefore, there is a God who first put the universe into motion.
Similarly, Aquinas discusses efficient causes. An efficient cause is what we simply refer to as a cause, in other words that which causes an action or event. The first efficient cause leads to

various intermediate causes and finally the ultimate effect. As we can in the universe, there is an ultimate effect, that is the universe currently existing. Therefore something caused this. It’s impossible for there to be an infinite string of efficient causes back in time without a first efficient cause. Without a first cause, there would be no following intermediate causes or ultimate effect because nothing would have caused them. Therefore, there was one first efficient cause of the universe. Aquinas argues that was God.
Lastly on that logic, Aquinas believes everything which currently exists also, at one point, did not exist.

This is because it’s possible for everything both to exist and not to exist, therefore both possibilities must have been fulfilled at some point. He phrases it in those terms, but I believe his argument is better understood by saying everything which exists must have come into existence, and therefore didn’t exist before that. Since something cannot spontaneously come into existence, he believes, another being gave everything else existence. This is called a “necessary thing,” meaning its existence is necessary for the existence of other things. Aquinas believes a being bestowed its necessity onto itself and did “not [receive] it from another.” What was a paradox before, an object being both the cause and effect, is now the logic. This object is God, and gave existence to all other

objects.
Next, Aquinas dives into linguistics. He notes the use of “more” and “less” in relation to various adjectives. Though he jumps a few steps in logic, I believe he’s arguing that if there is a scale of each adjective, like hot, in what is more or less hot. By having this scale, there is clearly something which is the most hot, or the hottest. His example here is fire as the hottest thing, being the cause of all heat in the world. This follows with all adjectives. Therefore, something must exist which is the most good, and the cause of all good in the world. He calls this object God.
Lastly, Aquinas discusses the tendency of unintelligent beings to act towards an end. While he provides no examples, I assume an example fitting his argument would be a plant bending to stretch closer to the sun, or roots bending to look for water. Since they typically reach the end, and the plant survives with sunlight and water, something must be controlling them as they have no ability to control themselves. He compares this to an archer aiming an arrow and hitting a target. While the arrow is what hit the target, the archer directed it just in the way that God directs the natural world.