London Ed demands that I reduce my circularity objection to a sound bite. No can do. But at least I can combat this travesty he ascribes to me:
The thin conception of 'exists' is that 'An F exists' means the same as 'The concept *F* is instantiated'
But if *F* is instantiated, then it is instantiated by an individual that exists
Therefore the thin conception of 'exists' is circular.
So let me try once more. I will try to be succinct. But there is no way I can get my point across in just a few sentences. Philosophy cannot be reduced to sound bites!
1. On the thin theory, 'An F exists' means the same as 'The concept *F* is instantiated.'
2. If a first-level concept such as *F* is instantiated, then it is instantiated by an individual.
3. Let the arbitrary constant 'a' denote an individual that instantiates *F.*
We now ask whether a exists, does not exist, both, or neither. These are the only options.
4. By LNC, a cannot both exist and not exist.
5. By LEM, a must either exist or not exist.
6. If a does not exist, i.e., if a is a Meinongian nonexistent object, then the link expressed in (1) between existence and instantiation is broken.
7. If *F* is instantiated, then *F* is instantiated by an individual that exists.
8. On the thin theory, 'An F exists' means the same as 'The concept *F* is instantiated by an individual that exists.'
9. A definition (analysis, account, theory, explanation ) is circular iff the term to be defined occurs in the defining term.
10. 'Exists' occurs both in (8)'s definiendum and its definiens.
11. The thin theory is circular.
Summary: Our question is: What is existence? The thin theory maintains that existence reduces to instantiation. The whole point of the theory is that existence is in no sense a property of individuals; what it is is a property of concepts, the property of having an instance. But if a first-level concept is instantiated, it is instantiated by an individual that exists. Therefore, the attempt to reduce existence to instantiation ends up presupposing what was to be reduced, namely existence, and is a failed theory for this reason.
Objection. (5) is false. Individual a neither exists nor does not exist. To exist = to be instantiatiated, and no individual is either instantiated or not instantiated.
Reply. This objection begs the question. The question is whether existence can be reduced to instantiation. One cannot just assume that it can be so reduced. Furthermore,it is a plain fact that individuals exist. I exist. This cat exists. And of course the existence of this cat is not its being instantiated. Since I exist, and my existence is not my being instantiated, existence cannot be reduced to instantiation.
The point could be put as follows. The thin theory tries to reduce singular existence to general existence. But general existence presupposes singular existence: there cannot exist cats in general unless this or that individual is a cat and exists. Therefore, singular existence cannot be reduced to general existence.
It may that what London Ed is doing is simply stipulating that 'exist(s)' shall mean 'is instantiated.' But an arbitrary stipulation gratuitously made can be gratuitously rejected. That individuals exist is a plain fact, innocent until proven guilty. The question about existence cannot be answered by any mere stipulative definition.