Thomism's Five Proof of God's Existence

Thomism is the school of philosophy that follows the teachings and ideologies of Thomas Aquinas, a Catholic theologian and philosopher. Aquinas combined Christian theology and Aristotelian philosophy to create a new ideology that has become among the most influential in history. This philosophy was embraced by both secular and theological philosophers. His writings were heavily endorsed by the Catholic Church to the extent that they were ranked second only to the Bible. His work Summa Theologica had a radical influence on medieval theology and is still being used by the Catholic Church today.

Thomism as a philosophy is opposed to blind faith practiced by most Christians. It is strongly rooted in reason and views the laws of causality and non-causation as the fundamental principles of reality. Thomism believes that most of what happens in nature can be viewed through the lens of reason and observation. However, it recognizes that there are some things that can only be revealed by revelation.

Another belief of Thomism is that humans can only know God through analogies and metaphors they can relate with. The reason for this is that we can never truly understand the Divine nature due to how God is infinite, eternal, and unique. On the basis of this, it believes that some parts of the bible can be interpreted figuratively.

While trying to prove the God’s existence, Aquinas gave the difference between existence and essence. He saw God as eternal and perfect, having absolute power which is in stark contrast to humans that are perfect and finite. Therefore, this shows that God is the only being whose existence is similar to his essence. To demonstrate God’s existence, he offered five proofs which we shall consider in this article:

The argument of the unmoved mover

In the world, things are always in motion. And it is only an object that is in motion that can push another object into motion. The first object itself was put into motion by still another moving object and so it continues. However, this process cannot reverse itself to infinity. Reason is that normally there would be no first mover which would result in no movement. Therefore, the only reasonable conclusion shows that a first unmoved mover exists which happens to be God. This argument was an attempt by Aquinas to explain the cause of change in the world. He got his inspiration from Aristotle’s concept of physics which studied change and motion in the physical world. In  the same way things are created by objects that were already in existence, that is how motion is also transferred from one object to another.  

The argument of contingency

There are perishable things in the world which exist today and are gone tomorrow. But if these things are left to chance and in the process go out of existence, then they would cease to exist if they are given infinite time. However, since things already exist, then there must be a being that is imperishable. This being is definitely God. Aquinas formulated this argument by studying how things exist and cease to exist in a short time. He argued that if everything in the universe could be destroyed, then there would come a time when everything we know would cease to exist. However, his research has shown that this is not the case as there is at least one thing that cannot go out of existence.

The argument of the first cause

In the world, nothing happens by chance as everything is caused. However, an object cannot be the cause of itself as this would indicate that the object existed before itself which is impossible. Therefore, if there is no first cause, there will be no second cause, and even final cause. In reality, this logic goes against what we already know in nature. Therefore, a first cause must exist which is not acted upon by anything else and that cause is God. The basis of this argument is the cardinal theory in physics which holds that every effect must have a cause. Using this theory, Aquinas believed since every object in the world was created out of something else, then the world came into being through a cause he identified as God.

The argument from degree

Humans naturally view things in the world according to some characteristics of different degrees which could be good, noble, or true. Also, some things are judged based on how good or bad they look.  However, this ability to judge only indicates that a kind of standard exists against which things are judged. For example, if someone is judged to be bad, then there must be a standard of good which the person has failed to live up to. Therefore, this standard is God. Aquinas developed this argument from studying Plato and Aristotle. He believed that objects with flawed or partial existence show that they are not responsible for their existence. Therefore, they have to rely on things outside of them for their existence.

The teleological argument

In nature, there are unintelligible and inanimate objects that behave in predictable ways and follow a set pattern. This behavior only shows that nothing is left to chance. However, since they are non-intelligent objects, they have no idea of how to program their behaviors or even set themselves. Thus, there is a being that is obviously responsible for directing and guiding them. And judging by the behavior of these objects, the mystery being is highly intelligent and knowledgeable. Thus, this being is definitely God.   In presenting this argument, Aquinas encourages his readers to take a look at the nature of the world and note how everything in it functions seamlessly without coordination. He believed that this did not happen by chance as there must be a designer who is responsible for designing and planning everything. Aquinas concludes that the world was designed by God.


In this article, we have looked at the case for the existence of God using the Thomism’s five proofs of logical argument. These proofs were popular in their day and are still being used by most theologians as a rational logic to defend God’s existence. Finally, according to Aquinas, since he has undoubtedly proven that God exists he could focus his attention to consider God’s work and nature.

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