Yeah. It just seems to me you haven't grasped the purpose of rigid designators.

I understand that you can stipulate that, on account of having been named, an entity can be imagined to have been different than they are in actuality. So I could be imagined to have been born a woman, for example. And according to the idea that my identity is established by naming (rigid designation) my identity is thereby hermetically sealed from alteration despite any and all conceivable alternate forms I can be imagined to have taken in other possible worlds.

But the limits to this cannot be coherently established. It might seem coherent to say I could have been born a woman, but what about the idea that I could have been a stone, a tree or a mountain? I think the inconceivability of this (absent the idea of a unique individual soul or essence or something like that) shows that description plays an ineliminable part in establishing identity, if not in merely stipulating it..

That just looks like a misconstrual of the way rigid designation works.

What if Janus had a haircut yesterday? What if Janus had never developed an interest in modality? What if Janus had been born a woman? What if Janus were a rock? What if Janus were not identical with Janus?

Some of these are possible worlds, some impossible worlds, and for different reasons. The semantics helps us sort them out.

What if Janus had a haircut yesterday? What if Janus had never developed an interest in modality? What if Janus had been born a woman? What if Janus were a rock? What if Janus were not identical with Janus?

Some of these are possible worlds, some impossible worlds, and for different reasons. The semantics helps us sort them out. — Banno

Sure we can try to imagine all those things and discover the special conditions we would need to posit to make them coherently imaginable (as opposed to merely saying them). But such things were done long before rigid designation ever became an explicit thing. Think about aboriginal myths, for example.

Sure.

Rigid designation is just a new term for something we've done all along. It serves to set out what we are doing, and to allow is to differentiate between certain modal problems in a way that allows us to dissipate or explain them.

That's true; and I have to agree it is helpful to make explicit to ourselves what we are doing. Perhaps I have been looking for more in the ideas of rigid designation and possible worlds than I should have.

Cheers. To be sure, there are folk who do think along those lines. But I think treating modality as mooted daydreams avoids most, if not all, of the various pitfalls ascribed to possible world semantics.

OK thanks, that's been helpful; you've altered my perspective re modal logic. :smile:

:wink:

Suppose X is not an actual world.
There has to be an reason why it's not actual (the principle of sufficient reason).
What does having a reason for X is not actual mean?
It simply means that we have an argument that proves X is not actual. If there's a proof for X is not actual, it implies X is necessarily not actual.
In other words,
1. If X is not actual then X is necessarily not actual.
2. If X is necessarily not actual then X is not possible.
Ergo,
3. If X is not actual then X is not possible (1, 2 HS)
Ergo,
4. If X is possible then X is actual (3 Contra)
QED — TheMadFool

given 1) ~w
given 2) ∀(~w) ∃(r): r => ~w
assume r, therefore ~w
Not a giant step for logic.

Please give predicates for "actual," "possible," "necessary." No predicates, no precision; no precision, no proof.

Please give predicates for "actual," "possible," "necessary." No predicates, no precision; no precision, no proof. — tim wood

:up:

1. If world X is not actual then there's a proof why world X is not actual. — TheMadFool

Not necessarily. There could be some true statements we can't prove (incompleteness)

2. If there's a proof that world X is not actual then necessarily world X is not actual. — TheMadFool

Wot? Max I'd be willing to say is "If there is valid proof that world X is not actual then we are justified in believing that world X is not actual"

4. If world X is not actual then necessarily world X is not actual. (1, 2 HS) — TheMadFool

But those premises are false.

given 1) ~w
given 2) ∀(~w) ∃(r): r => ~w
assume r, therefore ~w
Not a giant step for logic.

Please give predicates for "actual," "possible," "necessary." No predicates, no precision; no precision, no proof — tim wood

Why? Sentential logic works fine.

Not necessarily. There could be some true statements we can't prove (incompleteness) — khaled

You're bending over backwards, going to great lengths as it were, to make a point. You have to prove incompleteness whatever that means in your case.

Here's the deal. I present to you a world Z that is not actual.

The question: Why is world Z not actual?

You have to prove incompleteness whatever that means in your case. — TheMadFool

No I don't. You stated the premise that if something is true, we can prove it. Prove that premise. You think if it is true, there should be a proof for it, so where is the proof for that.

I don't need to definitively state or even prove that there are true, unprovable statements. Because I'm not making a case here. You have a dubious premise in your argument, you need to back it up. It is not at all obvious that every true statement has a proof, not since Godel.

Here's the deal. I present to you a world Z that is not actual.

The question: Why is world Z not actual? — TheMadFool

Here is the deal. I present to you a red car.

The question: Why is this car red?

Answer that and I'll tell you why Z is not actual.

Here is the deal. I present to you a red car.

The question: Why is this car red?

Answer that and I'll tell you why Z is not actual. — khaled

:lol: I have not time for your silly games khaled

Please give predicates for "actual," "possible," "necessary." No predicates, no precision; no precision, no proof
— tim wood
Why? Sentential logic works fine. — TheMadFool

All right. What exactly do they mean - as you're using them?

Doesn't it equalise itself, God does and doesn't exist? Do you see the paradoxical effect?

The only worlds where God actually exists are not equalised by an amount of worlds where God doesn't.

So how does God exist, if equally he doesn't?

How is that paradox if there is no certainty nor self-contradiction?