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Arguments for the Existence of God

Philosophy of Religion

The Ontological Argument (Anselm of Canterbury)

Information: A brief review of Bishop Anselm's version of the Ontological Argument. All quotes in this article are from Anselm's Proslogion, unless otherwise noted. A version of this article was originally published on the website You Tube icon - Copyright Fasticon (Freeware) There is a revision quiz available for this topic

Key terms

  • Ontology: To do with what something really is.
  • Epistemology: To do with 'knowledge' (or what we claim to know about something).


'I [do not] seek to understand so that I can believe, but rather I believe so that I can understand.' [Bracket mine]

The Ontological Argument for the existence of God was first (and famously) set out by Bishop Anselm (1033-1109), in his Proslogion (Chapters 2-4). Ontological arguments are basically thought experiments, whose intention is to demonstrate the reasonableness of believing that something (logically) exists. When used in theology, they are intended to show that it is logical to believe that God exists (or illogical to believe that God does not).

Someone thinkingAs an exercise in logic, ontological arguments do not refer to data or evidence from the way the world is, in the same way that Design Arguments and Cosmological Arguments do.

In terms of trying to prove God's existence, the Ontological Argument only seems to achieve this if one first supposes that God exists. However, this would mean that they were circular (and unsound). Such an idea led the Swiss theologian Karl Barth (1886-1968) to claim that as a Christian (and someone who already believed in God) Anselm could not have been intending to present an argument for the existence of God based on this means, but was merely reflecting on the wonder and nature of God.

The key idea

'God is that than which nothing greater can be conceived'

Anselm's Ontological Argument is about whether 'existence' is an attribute (or quality) of God, in the same way that omnipotence, omniscience and benevolence are believed to be. Anselm often refers to God as the 'greatest conceivable being', but this is not like saying God is the most powerful (omnipotent) or the most knowledgeable (omniscient) Being imaginable. Instead, it is more to with thinking about the one thing God necessarily has to be - which for Anselm is that God has to be existing (or exists)!

In his 'argument', Anselm also touches on the relationship between what we know (epistemology) and what something is (ontology). In fact, the logical-connector he uses to conclude that God exists, is that we cannot have an idea of something unless it first exists!

For Anselm, something that exists is better than something we can only imagine existing (i.e. existence is the 'greatest' quality something can have). Although one can imagine all kinds of fantastic creatures, if they do not exist then they cannot be the greatest of all conceivable beings (according to Anselm).

So for Anselm, anything which has the attribute (or quality) of 'existence', is far greater than something which does not have this. Therefore, in saying that God is that than which nothing greater can be conceived, Anselm is simply saying that the best thing we can think about in terms of God, is that God exists.

Something to think about and discuss: Is the best thing we can conceive about something, is that it actually exists? What about if this was a malevolent being? Is it also true that everything we can imagine, actually exists?


First statement

Anslem presented his 'argument' in two stages. In the first, he makes the claim that 'existence' is the greatest quality God can have. In order to illustrate this, he asks the reader to think about whether a picture someone has thought about painting, is greater than the one they have actually painted:

Artist palette'For when a painter thinks ahead to what he will paint, he has that picture in his thought, but he does not yet think it exists, because he has not done it yet. Once he has painted it he has it in his thoughts and thinks that it exists because he has done it; And certainly that greater than which cannot be understood cannot exist only in thought, for if it exists only in thought it could also be thought of existing in reality as well, which is greater.' [Emphasis mine]

Second statement

The second statement expands on the first, and is the idea that the greatest thing we can imagine about God is not only that God exists, but that it is illogical to imagine God not existing:

'For one can think there exists something that cannot be thought of as not existing [or it is inconceivable for it not to exist], and that would be greater than something which cannot be thought of as not existing [i.e. It does not exist!]; For if that greater than which cannot be thought can be thought of as not existing, then that greater than which cannot be thought is not that greater than which cannot be thought.' [Emphasis and brackets mine]

In other words, the greatest possible thought one can have about God, is not only that God exists but that God's non-existence is impossible (or one cannot conceive of any realm of existence (or possible world) where God does not exist).

Anselm is actually arguing that God has necessary existence, and as a being which has necessary existence this would mean God necessarily exists in all possible worlds.

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