## Tuesday, August 14, 2012

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Does premise 5 mean that you might not have been the same as you are, or that you might not have been the same as you were?

I agree that nothing is (actually) not the same thing as it (actually) is, but I'm not sure if that entails that nothing could have not been what it (actually) is.

So I think it makes a difference whether we read premise 5 to mean that you might not have been the same thing as you might have been, or to mean that you might not have been the same thing as you (actually) are. On the former reading, it goes through, but on the latter reading, I'm not so certain.

The question is whether you could have existed without being the same as yourself -- and I say you might have existed without being the same thing as you actually are, so long as you would not have been a different thing than you would have been (what you would have been would in that case be different a different thing than what you actually are).

Sorry if I'm not putting this very clearly, but I'm confused by the phrase "self-diverse".

Thanks for the post.

I wonder if you might not run into this difficulty: you are saying that it is not possible that I be not self-identical, which amounts to saying that it is necessary that I am self-identical. But it is possible that I not exist. So at some possible world W, I do not exist, but am self-identical. But, surely, if at W something is identical with Leo, then Leo exists at W. So, it would appear that your assumptions land you in a contradiction (that at some possible world W, I both exist and do not exist).

OK, so existence is not captured with a equals sign.

What would

(Ex) (x)

mean? Would that work?

William,

Identity, not equality.

'(Ex)(x)' does not express a complete thought. 'For some x, x' is neither true nor false. 'For some x, x =x' expresses a complete thought, and is true, but not the same thought expressed by 'Something exists.'

Leo,

You are necessarily self-identical, but not a necessary being. In possible worlds jargon: in every world in which you exist, you are self-identical; but you do not exist in every possible world.

I don't see any contradiction.

You are necessarily self-identical but contingently existent. I conclude that existence is not self-identity.

Of course, when I say that you are necessarily self-identical I do not mean that every world W is such that you are in it and self-identical; I mean that every world you are in is a world in which you are self-identical.

Alex,

The point I am making is very simple. It is true that I might not have existed; it is not true that I might not have been self-identical. So existence is not self-identity.

Dr. Vallicella,

But then it seems you're illegitimately shifting the sense of "necessary" and "possible": in (2) you are using "possibly" to mean that there is some accessible possible world in which I do not exist, but in (6) you are using "possibly" to mean that there is some accessible possible world in which I exist and at which I am not self-identical. Surely, "There is an accessible world at which p" and "There is an accessible world at which I exist and p" are not equivalent. If you were to use one sense of "possible" consistently, you would need to reject either (2) or (6).

In other words, if what you mean by "necessarily self-identical" is that "every world you are in is a world in which you are self-identical," then by parity of reasoning "necessarily existent" should be construed as "every world you are in is a world in which you exist," which would render (2) trivially false.

Well, in (6) I don't use 'possibly.' Do you mean (5)?

If you don't accept the reasoning, tell me which premise you reject or which inference you consider invald.

Leo,

What's the alternative? That at all worlds where you do not exist, you are not self-identical? (if existence is self-identity, then that seems to follow) Well, at those worlds where you do not exist, what is it that is not self-identical anyway? In a domain with everything but Bill, what is the truth-value of "Bill is self-identical"? "Bill is not self-identical"?

Hrod,

The alternative is that in a world in which I do not exist, I am distinct from everything, which does not imply that I am self-diverse in that world, since I don't exist there.

But, as you seem to appreciate, there must be something in those whorlds in which I do not exist that represents me there so that it can be true there that I do not exist. See my latest post for details.

Again, I am agreeing with you all the way here. Existence is not self-identity. It is, of course, the instantiation of a singular concept. But there we disagree.

Ed,

Partial agreement is better than no agreement!

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