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Anselm's Ontological Argument - PPS


Anselm’s ontological argument attempts to prove God’s existence from a priori knowledge. This means that once a person knows the definition of God, then it is self-evident that God exists. Anselm’s argument can be broken down in the following way:

1. God is ‘something than which nothing greater can be thought’ (Anselm, 2007, p. 84).

2. As an object of thought, God exists necessarily in the mind.

3. Something that exists in reality and in the mind is greater than something that only exists in the mind.

4. God must exist in reality and in the mind.

Premise one provides a definition of God. Anselm elaborates on this definition in his Monologion where he gives the following argument (Anselm, 2007, p. 7-8).

1.1. There are certain goods that are unequal in their goodness either by degree or by mode.

1.2. These different goods can only be compared by something that is common to them all.

1.3. What is common to all things which are said to be good, is goodness itself.

1.4. Whatever is good in itself is greater than what is only good through what is good in itself.

1.5. Goodness itself is supremely good (which we can also call supremely great). This is what we call God.

Premise 1.1 is known through observing those things which are called good. A horse can be called good by its strength and also by its speed. These are two different modes of goodness, as strength and speed aren’t the same as each other. However, a horse that is faster than another can be said to be better by a degree of goodness in so far as it is good for a horse to be fast. Premise 1.2 is intuitive as the act of comparing must be by a certain characteristic that two or more things are said to have in common. Premise 1.3 argues that what is common among things that all have the characteristic of being good must be the characteristic they share in common, i.e., being good. Premise 1.4 argues that whatever participates in goodness will be less good than the source of that participation. Since goodness itself is the source of all that participate in goodness, and everything is contingent on their source, goodness itself will be greater in goodness than whatever participates in it. Premise 1.5 follows from the prior premises.

Premise two of Anselm’s ontological argument necessarily follows from the definition of God. If God is defined as ‘something than which nothing greater can be thought’, by understanding this definition, God then becomes a thought in the mind of the person understanding. By being a thought, God then exists in the thinker’s mind. Even the person who doesn’t think God exists in reality must agree that the ‘God’ they are thinking about exists in their mind.

Premise three of the ontological argument argues that something’s existence is greater when it has more of it than if it has less of it. As existing in reality and in the mind is more of an existence than just existing in the mind, then it can be said to be greater.

Premise four follows from the prior premises since if God only existed in the mind, then there could be something thought of as being greater than that, which is something that exists both in the mind and in reality. However, since the definition of God is ‘something than which nothing greater can be thought’ this greater being which exists in the mind and in reality would then be God. Therefore, God exists both in the mind and in reality.


Anselm’s ontological argument appears sound on first impression; however, the very definition of God in the argument is the most problematic since it doesn’t follow that this God would exist. If God is “something than which nothing greater can be thought”, then the greatness of this God is limited to our thought. Imagine that instead, there was a thing whose greatness transcended human thought to the point where we couldn’t even think about it. This being would be greater than Anselm’s God because it is not limited to the capacity of being an object of thought. However, within Anselm’s definition, his God would not be contradicted by this greater incomprehensible being since this greater being cannot be thought. While it’s impossible to think of this superior being, we can at least know that if being an object of thought is a limitation, then this second God is greater than Anselm’s God, although we are unsure of how it could be greater.

Plantinga gives us a solution to this problem by getting rid of thought as the basis for claiming existence and instead shifts the focus to possible worlds.[1] In Plantinga’s version of the argument, this superior incomprehensible God would exist instead of Anselm’s. However, even Plantinga doesn’t believe that his argument proves God necessarily, but that it is a rational argument for believing that God exists. Instead, I will try to formulate an ontological argument that proves necessarily (so long as you agree with the definition) that God exists.

1. God is existence.

2. Existence exists.

3. Therefore, God exists.

This may seem like an overly simplistic argument that doesn’t prove anything, but there are grounds for believing that this ontological argument proves the existence of a God a priori, and further arguments can prove which understanding of existence is best considered as the maximally greatest being. There can be no sound objection to premise 2 as any objection would have to predicate an existent or admit that the objection itself is an existent. The mere fact of existents depends on the truth of premise 2, and thus relying on existents for an objection already proves premise 2.

Premise 1 is not an unpopular definition of a monotheistic God. As shown in Figure 1, pantheists hold that the universe or the totality of existence is identical to God, classical theists believe that the essence of God is existence as distinct from the universe, and panentheists believe that God is both the universe and transcends the universe.[2]

Figure 1 – Views of God and Existence.

While pantheism, panentheism and classical theism are not comprehensive of all views of God, it seems that for our definition, there is quite a bit of support for using it. This ontological argument doesn’t necessarily prove the existence of Anselm’s God as there would need to be further arguments for the classical theist’s understanding of existence as transcendent and separate to existents. However, this ontological argument does commit someone to God’s existence.

I don’t believe ontological arguments can help us move from theism to classical theism, instead we must use cosmological arguments. This is because a classical theist’s definition of God is as something that is wholly transcendent to us and is, therefore, beyond our purely intellectual understanding. This means we can’t comprehend God’s essence, but instead need to rely on forming analogies to God’s essence from the world around us. While cosmological arguments rely on arguing from a posteriori knowledge, and are not as compelling as a priori arguments like the ontological argument, they can still provide a rational and intuitive basis for accepting classical theism.


Anselm, Basic Writings, translated and edited by Thomas Williams (Indianapolis: Hackett Publishing, 2007).

Aquinas, Thomas, Summa Theolgiae, ed. by John Mortensen and Enrique Alarcón, trans. by Laurence Shapcote, (Lander, Wyoming: Aquinas Institute for the Study of Sacred Doctrine, 2012).

Plantinga, Alvin, The nature of necessity, (Oxford: Clarendon, 1992).

Spinoza, Benedict, Ethics, translated and edited by Edwin Curley (New York: Penguin Books, 1996).

Tillich, Paul, Systematic Theology Vol. 1, (Chicago: University of Chicago Press, 1951).

[1] Alvin Plantinga, The nature of necessity, (Oxford: Clarendon, 1992) p. 213-221. [2] For a pantheist definition see, Benedict Spinoza, Ethics, translated and edited by Edwin Curley (New York: Penguin Books, 1996) p. 16; for a panentheist definition see, Paul Tillich, Systematic Theology Vol. 1, (Chicago: University of Chicago Press, 1951) p. 235-7; for a classical theist definition see, Thomas Aquinas, Summa Theologiae, Ia, Q. 3, A. 4.

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