By: Rachel Lyle, May 26th, 2017

Here is another paper I had to write for my Philosophy class.

Thomas Aquinas in Summa Theologica argues the existence of God with an A Posteriori Cosmological Argument. In his second way argues from observable facts, efficient causation exists, to the conclusion that a first original cause necessarily exists. In this paper I will argue that Aquinas’s argument, even if valid and sound, does not prove the necessary existence of a 3- O God as efficient causation.

Aquinas’s argument, if valid and sound, does not prove the existence of an actual 3-O God. Aquinas uses an A Posteriori Cosmological Argument to prove his conclusion is true. An A Posteriori argument is an argument that uses prior knowledge from the observable world to provide its reasoning. A Cosmological argument is an argument for the existence of God saying that all things that existing depend on something else for their existence therefore there is a necessary being that the whole of creation depends on for it’s existence. A 3-O God is a god who is Omniscient, Omnipotent, and Omnibenevolent. Omniscient means someone is all-knowing or all-seeing. Omnipotent means someone is all-powerful, able to do anything, has unlimited power. Omnibenevolent means someone is all-loving, all-good, infinitely good. The cosmological argument uses facts from the observable world to conclude that there is an original efficient cause that started the universe proving the existence of a 3-O God. Efficient causation is something that brings something into being or creates change.

The argument that Aquinas uses is stated in the premises that follow. Efficient causation exists in this universe, meaning everything in the universe has a cause. Everything in the universe has a cause a part from itself, in other words nothing currently in existence can cause itself or be its own cause. So either there was a first original cause outside of everything in existence or the chain of causes is infinite, something caused everything in existence to be in existence or the causes go back forever and ever. An infinite regress of causes is impossible or it is impossible for the chain of causes to go back in time forever and ever. This leads to the conclusion that there is a first original cause, therefore, something outside of the universe had to cause the universe.


Saying that everything has cause outside itself, therefore efficient causation or an original cause exists is a Quantifier Shift Fallacy, the mother of all fallacies. A Quantifier Shift Fallacy is reversing the order of two quantifiers, every A has related B, there is some B related to every A. An example of this would be everyone loves someone, therefore There is someone that everyone loves. It’s true if you remove the cause you have no effect, So there have been a first cause, or A because A leads to B leads to C eventually leading to X. If there is no A there is no X. X exists, therefore logically there had to have been an A, but how do we know that it was not an infinite regress and no A exists. This cause may have happened but infinite regress could have happened because this argument that an infinite regress of causes is not possible is like saying that it is impossible for anything to go to infinity. The example of numbers can be used to illustrate how this is not true. There is an infinite amount of numbers, they go on forever and ever in both positive and negative quantities, therefore it shows that it is possible to have an infinite regress of something.

The premise that either there was a first original cause outside of everything in existence or the chain of causes is infinite, and an infinite regress of causes is impossible is a Disjunctive Syllogism, which means, either P or Q, not P therefore Q. This is a false Disjunctive Syllogism because he has no back up or basis to found this premise on. We have no proof that the first cause was a being and not an event or a first cause. Aquinas also does not state that this first cause is a being and has no proof to show that it was a being that started everything, therefore this causes his argument to fall apart. The original cause might have been an event outside of the universe, such as the Big Bang, which was necessary for the rest of the universe to happen. If it were a being then that being would have had to act on the universe. The being is outside the universe but if a being is outside of the universe it cannot act on the universe, therefore it could possibly have been an event rather than a being. There may have been an event outside of the universe that was an original cause that caused the universe.


Thomas Aquinas in Summa Theologica tries to prove a 3-O God with an A Posteriori Cosmological argument. He uses a Quantifier Shift Fallacy to say that a first cause exists because everything that is in existence in the known universe has a cause outside of and distinct from itself and therefore an infinite regress of causes is not possible. An infinite regress is possible just look at numbers and their infinite continuation of both positive and negative quantities. He also has no proof or back for saying that this proves that a 3-O God exist, he has no proof because this argument never says anything about the first cause being God it just says something caused every other cause therefore his argument falls apart. This shows that it does not mean that a being started the universe and that it could have been an event that caused the universe. Therefore this argument, used by Thomas Aquinas, even if valid and sound, but does not prove a 3-O God.

Even if this argument does or does not prove the existence of God, it is and will always be my personal belief that you can not factually prove or disprove the existence of God. I believe that God exists in my heart and I believe that is truly all that really matters.