Could you summarize the logic of the Ontological proof?
Answer by Jürgen Lawrenz
There are actually different ones, but you asked for their logic, which I take to mean “do they stand up to strictly logical principles?” I’m afraid all of them are invalid under these premises — for which the main reason is that a proof can confirm knowledge we already possess, but cannot prove the existence of merely conceptual entities.
For example Descartes said: “I think therefore I am”. This is cast-iron, because the contradictory statement “I think, therefore I am not” is nonsense, even thought its logical form is identical to the former. But now Descartes goes on to claim that his essential self is as a “thinking thing”, implying that his body is a contingent (accidental) housing for the thinking thing. This logic is derived from the common belief that humans have a soul which inhabits a body, but is actually a separate entity. In principle it could therefore have been incarnated in any other body. It follows that the identity “Descartes” is a contingent fusion of his soul with a body that is his only in virtue of his soul having ensouled this particular body.
Now we don’t have any knowledge of bodies exchanging souls or souls wandering from one body to another. That’s the logical problem. Following Descartes we might now say, it is logically possible, although the probabilities are virtually 100% against it. But as far as proof is concerned, we cannot definitely rule out this possibility. A proof could only say, every human being is a union of soul and body; but then this proof is also problematic, because when the body dies, what happens to the soul? Here we have nothing other than conjectures to deal with — some biologists will say a soul is mortal and dies with the body; others might claim that there is no such thing as a soul anyway and refer to brain activity which stops when a body dies. Religions have a variety of explanations on offer as to what happens to the soul after death, but obviously these are not facts, but beliefs.
These consideration are all entangled in your question, because Descartes pins an ontological proof to his doctrine of the thinking thing. He still envisages it as “I”, which on the terms described above is already disputable — nevertheless he now says this thinking thing did not create itself, nor did it spring up from nothing (you might ask yourself at this point, is it truly logically impossible for a soul to come into being from nothing? Well, what is a soul? It is not a physical item, nor a form of energy: so what then?). Anyway, for Descartes, there is only one option left. An existent far greater than himself, a creative existent, a being like a soul but much more powerful, must have created it. This existent he calls “God” and declares the existence of God to be a necessary condition for these circumstances to arise.
This is not very compelling. Hostile critics pointed out that the evil demon who whispers in his ear is also a spirit and might have created his soul. Shock, horror! Moreover this demon nowhere refers to another demon co-existing with himself. But Descartes’ failed to consider these (logical!) possibilities, because they were not matters about which he could possibly think. Therefore, if we carefully consider these issues, we find that all his arguments are strapped to beliefs and opinions handed down by authority figures, which contrary to his fervent avowals he did not examine with a view to holding them false.
Now as mentioned above, a proof cannot certify existence without the existent being unambiguously defined. Yet all of Descartes’ arguments are inferential — “If A, then B”, where A and B cannot be proved independently. It is the case (as Wittgenstein once remarked), that if you use metaphysical diction, there will be signs in your sentences which have not been given an undisputed meaning.
Descartes was not the only philosopher dabbling in ontological proofs. So I will mention two other concepts, though very briefly. The cosmological proof starts from the assumption that “I can imagine that the universe did not exist until it was created”. Therefore a creator is necessary, etc. etc. I would question if anyone could truly imagine a non-existent universe (what kind of an image would it produce in the mind?).
The argument from design is similarly deficient, as it proposes that everything in the universe shows signs of planning. A big assumption! If you say, “prove it to me”, you might be handed an encyclopaedia of all the objects in the world with pointers to their interconnection. The trouble here is, that we are predisposed to see order, whereas it is entirely (logically) possible that this the universe is purely an outcome of chance (cf. Einstein: “God does not play dice.” Bohr: “Stop telling God how he should run the world!”).
As it happens, Kant examined the logic of the four main ontological proofs and demonstrated that all hinge on the credibility of what is called a “common notion”. For Christians such a common notion is God, for atheists that God is an empty concept. Accordingly both proofs based on these notions run their identical course to opposite conclusions.
No need to pursue this further, I believe. It suffices to note that the terms used in ontological proofs revolve around ‘possibility’ and ‘necessity’, of which it has to be said that we humans tend to overshoot the mark quite frequently, posing as God’s apprentices already endowed with his omniscience.
By the way: The technical terminology for these kinds of usages is “commitment to an ontological vocabulary whose sole purpose is to justify hyperintensional operators”. This is also worth taking on board!