An interesting take on the Ontological Proof.
As provided by Sean Carroll on Cosmic Variance, using formal logic.
I’ve never really talked about this proof for the existence of God, provided originally by St. Anselm of Canterbury, but essentially it goes like this:
When we hear the words “that than which a greater cannot be thought”, we understand what the words convey, and what we understand exists in our thoughts. This then exists either only in our thoughts or both in thought and reality. But it cannot exist only in our thoughts, because if it existed only in our thoughts, then we could think of something greater than it, since we could think of something than which a greater cannot be thought that exists both in thought and in reality, and it is a contradiction to suppose we could think of something greater than that than which nothing greater can be thought. Hence, that than which a greater cannot be thought exists both in thought and in reality. Therefore, that than which a greater cannot be thought really does exist, and in later chapters of the Proslogion Anselm argues that this being has the traditional attributes of God like being the omnipotent creator.
I’ve always thought this was kind of dumb, since it seems to fit well into the internet meme that goes like this:
1. We all know there is something of which a greater thing cannot be thought.
2. Something which exists in reality is better than something which exists in our thoughts.
4. Therefore god.
Now, it’s possible that others have a more mature take on this, as below.
It’s instructive and fun to see this in terms of formal logic, especially because the proof requires modal logic — an extension of standard logic that classifies propositions not only as “true” or “false,” but also as “necessarily true/false” and “possibly true/false.” That is, it’s a logic of hypotheticals.
Check it out.