Ontological Argument of God's Existence

When we think about the world we live in, we rarely have time to think on whether or not there is a God. Science has advanced rapidly since the last century. We have surpassed our ancestors unanswered questions on the laws of nature. Amidst our vast knowledge of the universe, we have trouble providing proof that God exists. The ontological argument argues the existence of God based upon the meaning of the term ‘God’.

Saint Anselm believed that the mere contemplation of God, proved that he existed. By definition, God is something of which nothing greater can be thought, therefore He must exist.
“For something can be thought to exist that cannot be thought not to exist, and this is greater which can be thought not to exist. Hence, if that-than-which-a-greater-cannot-be-thought can be thought not to exist, then that-than-which-a-greater-cannot-be-thought is not the same as that-than-which-a-greater-cannot-be-thought, which is absurd.”[1]
Here, the Saint points out that we can think of God as existing or not existing. If God is a being of which nothing greater can be thought, which would be greater - the mere thought of a Supreme Being, or a Supreme Being that actually exists?

Descartes tackled this same argument slightly differently. His argument stated,
“God is God.
If God were not perfect, he would not be God.
Therefore, God is perfect.
If God did not exist, he would be less than perfect than if he existed.
Therefore God is perfect.”[2]
The course manual goes even further to explain that Descartes believed that God possessed a property of existence and without that property, He would not be God. These fundamental characteristics are as fundamental as water being composed of two hydrogen molecules and one oxygen molecule. By definition, water is H2O and if any or these properties change, then it is no longer water. Since God is perfect by definition, he must exist, as existence is crucial to the definition.

Ironically, Saint Thomas Aquinas rejected this proof of God’s existence. However, his fourth proof of God’s existence in The Summa Theologica is closely related. This proof closely relates everything belonging to a universal gradation. He further explains that there must be a maximum to each genus:
“Now the maximum of any genus is the cause of all in that genus; as fire, which is the maximum of heat, is the cause of all hot things. Therefore, there must also be something which is to all beings the cause of their being, goodness, and every other perfect; and this we call God.” [3]
If we grade all things, there must be a maximum for the genus of ‘all things’, which would be an omnipotent being.

Saint Thomas Aquinas’ argument does not take the same path as Descartes or Anselm because there is no talk about the definition of the term God. However, he does make mention that God exists because he is the maximum genus of all things, making him the most good and perfect being in existence, which intermediately points to the same conclusion.

These arguments are based on the definition of the term ‘God’. The argument is indeed valid, however the premises may not all be true. If the definition that God is something of which nothing greater can be thought, then indeed the conclusion is true. However, if we do not accept the definition of God, the argument would not be sound. Similarly, if one rejects that the maximum gradation of genus of all things must be omnipotent, or that there must a gradation of all things, then the argument holds no water. The ontological argument is a perfect argument for those who already have faith that God exists. A skeptic, on the other hand, will find fault quickly, by rejecting the definition given for the term God.


[1] Saint Anselm, Proslogion 88
[2] Adam Morton Philosophy in Practice: An Introduction to the Main Questions (Cambridge MA: Blackwell, 1996), 54
[3] Saint Thomas Aquinas, The Summa Theologica, 26