St. Thomas of Aquinas was also a Christian philosopher and theologian, who came up with the “five ways” in his Summa Theologica. The five ways serves as a way to explain God and prove his existence based on what we experience through nature because he believed that in order to prove the existence of God, to people, he must be able to relate it to themselves. Aquinas believed that Anselm’s flaw must be addressed, and so he bases his five ways off of the ontological argument. The five ways are as follows: argument from motion, argument from efficient causes, argument from possibility and necessity, argument from gradation of being, and and argument from design.
Argument from Motion
In order for something to be put in motion, it must be set in motion by something else, either supernatural, or of a different type. The first mover has to be God because the mover has to be a supernatural (be not natural, for example: humans, animals, etc.) being and exist outside the natural world, or be of a different type. And in order to set everything else in motion, He must be of a different type than everything else.
Argument from Efficient Cause
Everything in nature requires a cause, something that is outside of the being itself. The efficient cause means that everything in nature requires a cause, which is outside of the being (like an external force, something that exists on its own) and it is necessary to arrive at the first efficient cause, which St. Thomas says is God. If there is not a first cause, simply nothing will happen because everything in nature requires a cause, like an illness for example, is caused by bacteria, and the spread of bacteria.
Argument from Possibility and Necessity
In nature there are possible beings that are possible because of the one necessary being. Possible beings are what is possible through the necessary being, which is God. What this means is that the necessary being is something that must exist because without it, much like the first mover, and the first cause, nothing can happen. There are only possible beings because of the necessary being.
Argument from Gradation of Being
There are beings that are “more” or “less”, the level depends on a being that is the cause of the goodness. What this means is that the cause of goodness is something to which creates and idea which we compare everything else to, for example cold is not an independent property, cold is instead, the lack of heat, but heat itself is the independent property, so when we are talking about how cold something is, we are talking about the lack of heat in it.
Argument from Design
Nature lacks intelligence, but every being is directed to its end (goal). The being which directs beings to their end is God. Basically, nature is being led to its end, and the one leading them is God.