Aquinas: The Ontological Proof

If you’ve done any philosophy in the past, you’ll probably be aware of Anselm’s ontological argument for the existence of God. It goes something like this: if you imagine the greatest being that could exist, it would have ‘existence’ as one of its qualities – because something that does exist is greater than something that doesn’t. Because ‘existence’ is one of the qualities of the greatest being, if it doesn’t exist (that is, if it doesn’t have ‘existence’ as a quality), it’s not the greatest being. Therefore, Anselm argues, the greatest being (ie God) must exist, simply by definition. Anselm lived in the 11th century; by the 13th, Aquinas was taking shots at his argument. 

I’m looking at 1a.2.1, titled ‘Is it self evident that there is a God?’ Aquinas introduces what seems like a quick version of Anselm’s proof:

“Once we understand the meaning of the word ‘God’ it follows that God exists. For the word means ‘that than which nothing greater can be meant’. Consequently, since existence in thought and fact is greater than existence in thought alone, and since, once we understand the word ‘God’, He exists in thought, He must also exist in fact.”

If you’re the greatest being, you exist in thought and fact, because existing in both is better than just existing in thought – so you’re not really the greatest if you don’t exist. Therefore, the greatest being exists by definition.

There’s a few other things that Aquinas is dealing with in his response to this proposition, so he doesn’t only talk about the ontological proof. For example, he talks about the definition of ‘self-evident’, pointing out that some things are only self-evident when you know the meaning of the terms involved, while others are self-evident in a more commonplace way. So we might say that a femur is a bone, and that’s only self-evident once you know that femur means ‘one of the bones in your leg’. The self-evidence of the proposition is dependent on understanding the terms. Alternately, we might say that some things are self-evident to everybody just because the relevant ‘terms’ are understood by everyone. We might say that ‘things are pulled downwards’: that’s self-evident in the sense that we all know what ‘things’, ‘pulling’, and ‘downwards’ are.

To me, this ends up undermining the idea of ‘self-evident’. If all ‘self-evident’ means is that you can generally figure things out when you have all the proper terminology and experiential evidence, then that’s fine. I mean, it seems like you can apply it as a definition to literally everything, which makes it redundant, but it’s a fine definition. My point is that ‘self-evident’ in its more traditional meaning of ‘not needing to be explained; obvious’ seems undermined here. It’s more a comment on the position of the viewing subject rather than telling us anything about the knowledge itself – so some physics proposition might be entirely ‘self-evident’ to a trained physics professor with 50 years experience, but that doesn’t really tell us anything about the proposition. It just tells us that the professor’s in a place where that proposition doesn’t need any explaining. Similarly, the concept of colour might be ‘self-evident’ to your average Joe, but not to a blind person. It becomes a comment on the position of the viewing subject, rather than telling us anything about the information.

So Aquinas argues that although God may be self-evident in Himself, that doesn’t necessarily mean we possess the necessary information to discover this self-evident thing. I think if that’s your definition of ‘self-evident’, then the term is functionally useless. Anyway, he goes on to slam Anselm’s ontological proof:

“…even if the meaning of the word ‘God’ were generally recognised to be ‘that than which nothing greater can be thought’, nothing thus defined would thereby be granted existence in the world of fact, but merely as thought about.”

Even if we accept that definition of God, Aquinas says, that doesn’t mean that the greatest being actually exists. It’s more saying that if the greatest being existed, it would have existence in fact as a characteristic, as the greatest being would not be the greatest being if it only existed in thought. That doesn’t mean we’ve accepted the initial premise that the greatest being exists!

“Unless one is given that something in fact exists than which nothing greater can be thought… the conclusion that God in fact exists does not follow.” 

Let’s rephrase Anselm’s argument in a different way:

  1. Let’s hypothesise the characteristics that the greatest being would have, if the greatest being did in fact exist.
  2. It would have existence in thought and fact as characteristics, because something which exists in thought and fact is better than something which only exists in thought.
  3. If the greatest being exists, it must have existance in fact as a characteristic. It is not enough for us to be able to imagine it: it must actually exist in order to be the greatest.

That’s more reasonable. It’s rephrasing his argument in a clearer way to avoid his false conclusion.

So this whole thing is sort of interesting, because often Anselm is held up as an example of how Christianity is nonsense. I’ve had people disprove the ontological argument and then sort of implicitly assume that Christianity is rubbish because Anselm’s ontological argument doesn’t hold water – as if we’re some huge philosophical monolith that stand or fall on the strength of one asshole’s ‘proof’. From that perspective, it’s cool that Aquinas is shitting on Anselm, because it highlights the differences within Christianity. It’s not I’m claiming this argument or that argument to be correct, I’m just noting that Christians aren’t necessarily intellectually compromised just because of their faith. It’s still possible to be logically rigorous. There’s also 2000 years’ worth of differences and doctrines – it’s not monolithic. All of these things should be pretty obvious to believers already, but it’s interesting to see practical evidence of the fact play out in reality.


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