Do Aquinas’s Five Proofs for the Existence of God Hold Up?

Updated on August 8, 2018
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Jennifer Wilber works as an ESL instructor, substitute teacher, and freelance writer. She holds a B.A. in Creative Writing and English.

Do Aquinas’s Five Proofs for the Existence of God Hold Up?
Do Aquinas’s Five Proofs for the Existence of God Hold Up?

Thomas Aquinas and the Proof for God’s Existence

According to the 13th-century Catholic philosopher and theologian St. Thomas Aquinas, the existence of the natural world requires the existence of God. He uses his own five proofs for the existence of God, or “the five ways” to prove his theory that God exists, and that the natural world can only exist if God exists. But is there any proof that his proofs for the existence of God are true? Believing his claim that God exists based on the "proofs" that he made up himself makes no more sense than believing that what the Bible says is true simply because the Bible says that itself is true.

Detail from "Triumph of St. Thomas Aquinas over Averroes" by Benozzo Gozzoli (1420–97)
Detail from "Triumph of St. Thomas Aquinas over Averroes" by Benozzo Gozzoli (1420–97) | Source

What are the Five Ways?

St. Thomas Aquinas outlined five ways to prove the existence of God. He claims that these “ways” prove that a God must exist for the universe and nature to have come into being.

Prima Via: The Argument of the Unmoved Mover

According to the first way, we can see that at least some things in the world are constantly changing. Whatever is changing must be changed, or moved, by something else. Whatever is changing it is itself changed, so it too is being changed by something else. This chain of changers or movers cannot be infinitely long, so there must be primary changer that causes change without itself changing. This, according to Aquinas, must be what we understand to be God. Since a potential doesn’t exist yet, it can’t cause itself to exist and so can only be brought into existence by an outside mover, whom already exists. According to Aquinas, "[t]he mover and the thing moved must exist simultaneously".

Secunda Via: The Argument of the First Cause

The second way states that, though we can see that things are caused, it is not possible for something to be the cause of itself because this would mean that it existed prior to its own existence, which is a contradiction. If something is caused, then the cause must also have a cause. This cannot be an infinitely long chain, so there must be a cause which is not itself caused by anything further; a first cause. This is what we understand to be God, according to Aquinas’s theory. The causes need not be sequential events. Aquinas argues that the first cause is first in a hierarchy, rather than sequentially. The first cause, or God, is a principal cause, rather than a derivative cause

Tertia Via: The Argument from Contingency

The third way says that we see things that are possible to be and possible not to be, or perishable things. However, it everything were contingent and, and so, capable of going out of existence, then, given infinite time, this possibility would be realized, and everything would cease to exist by now. But since things clearly do exist right now, there must be something that is imperishable. According to Aquinas, this necessary being is what we understand to be God.

Quarta Via: The Argument from Degree

According to the fourth way, things in our world vary in degrees of goodness, truth, nobility, etc. There are sick animals and healthy animals. There are well-drawn triangles and poorly drawn ones. Judging something as being "more" or "less" implies some standard against which it is being judged, so there must be something which is goodness itself, and this is what we understand to be God, according to Aquinas.

Quinta Via: Argument from Final Cause or Ends

Aqunias’s fifth way states that there are various non-intelligent objects in the world which behave in regular ways. This can’t be due to chance since, if it were due to chance they would not behave so predictable. Their behavior must be set, but it can’t be set by themselves since they are non-intelligent and do not know how to set their own behavior. This behavior must be set by something else, and that thing must be intelligent. Aquinas believes that this is what we understand to be God.

St. Thomas Aquinas, the 13th-century Dominican friar and theologian who formalized the "Five Ways" intended to demonstrate God's existence.
St. Thomas Aquinas, the 13th-century Dominican friar and theologian who formalized the "Five Ways" intended to demonstrate God's existence. | Source

Do Aquinas’s Five Ways Really Prove the Existence of God?

Aquinas claims that God is an unchanging source of change, and that for change to exist, there must be an unchanging source of change. There is no real reason that change must come from something that remains unchanged itself. It is possible to change something, and then be changed yourself.

Aquinas also claims that God must have always existed and will always exist. If God has always existed, where did he come from and how did he get there? Why is it necessary for the original creator to have always existed? Is it not possible that something could have existed, created something, and then stopped existing? For example, you were created by your parents, but they will stop existing eventually, just as you will stop existing eventually.

Perhaps the original ultimate force in the universe, AKA God can grow and change over time, just as the universe itself grows and changes over time. And perhaps the Universe will end one day only to give rise to the next universe and start the cycle over. If God never changes, neither will the universe, as the universe and God are one in the same. If nothing ever changes, then there is no purpose for the universe to exist. Aquinas was wrong in assuming that God must necessarily be some external force outside of the universe. Perhaps what we understand to be “God” is instead the universe itself, in all it’s ever changing, ever evolving glory.

Even if Aquinas was correct and there is some outside creator, there is no proof that this God is ultimately intelligent or perfect. If he were, everything he created should then be perfect. And since nothing in existence is perfect, then God cannot be perfect either. Assuming that God must be perfect and supremely intelligent is no different than a small child looking up to his parents and thinking that they are perfect and essentially God-like.

The universe and nature can exist without needing an external creator.
The universe and nature can exist without needing an external creator. | Source

No External Creator Needed

Of course, it isn't necessary for there to be an intelligent creator for the universe and the natural world to exist. It could have happened by chance. The argument that everything in nature is too complex to be chance doesn't hold up. For example, when life first appeared on Earth, there could have been any number of types of creatures that started to evolve, but only the ones that were viable lived on to continue to evolve. Perhaps there are lifeforms that can't survive in oxygen. Only life that can survive in oxygen would have continued to survive and evolve in the Earth’s present environment. Lifeforms simply adapt to their surroundings and only the ones that can survive do.

Life started out as single-celled organisms, but eventually grew to be more complex. The complexity of life arose very slowly as life adapted to become better suited to environmental conditions. Therefore, there doesn't necessarily have to be an intelligent mind creating everything in existence. The natural world does just fine without supernatural intervention.

The universe can create and change itself without supernatural intervention.
The universe can create and change itself without supernatural intervention. | Source

In Conclusion

Aquinas's five proofs don't hold up. There doesn't necessarily have to be an unchanging source of change, and unoriginated source of originated beings, a necessary source of unnecessary beings, an absolutely perfect source of all degrees of perfection, or an intelligent creator. The existence natural world does not require the existence of God, nor does it make the existence of God more probable. The universe and the natural world just are as they are, no outside help required.

Questions & Answers

    © 2018 Jennifer Wilber


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      • Miebakagh57 profile image

        Miebakagh Fiberesima 

        9 days ago from Port Harcourt, Rivers State, NIGERIA.

        Hello Jennifer, thank you for philosophical. You are in the same class with Aquinas. In reality, God does exists. If the creative materials of the world does not tell one that there is God (not there is a God), nothing can do. The fact that God did not change, will not mean that the creative universe will not change.

        My parents did not create me. They begot me. And, this applies to every person,includingyour goodself, right? If my parents change, and I see they change in some ways (that's to they likeing), and it means nothing to me. God is not a human being or like the material cosmos that he should change. He is creator.

        Let's take the potter as an example. The fact that he can break a mould pot and used the same materials to make another pot does not and will not prove that the Potter has change. He may only change his mind and direct it to do something else other then another. But he remained the same Potter, right?

        Thank you, and have a nice time.


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