What makes it rigidly designated? In every possible world Venus is X. But what is X? That "essentialness" of Venus? It is the causal conditions for which the term "Venus" is picked out amongst other things in the world. — schopenhauer1
"Venus" rigidly designates Venus becasue we choose it to work in that way; nothing more. We are using the word "Venus" to mean that exact same thing in every possible world in which Venus exists. There may be a causal chain leading to a baptism in the actual world, but there need not be any such causal chain in
every world in which Venus exists. Once it's "picked out", it is designated rigidly. I'm not sure if this is what you are saying, of if it disagrees with what you are saying. So Theseus' ship may change completely, and yet it continues to make sense to refer to it as the Ship of Theseus, using that name as a rigid designator.
is correct. I should have avoided the rock/window example, as it has lead to folk confusing physical and logical necessity. Quine is concerned here with logical necessity.
The question then is if we might want some notion of physical necessity (i.e., related to changing, mobile being) as an explanatory notion. — Count Timothy von Icarus
Not so much. Causation is a whole other topic.
You could consider "George Washington was the first President of the United States." Is it possible for this to become false? If not, then it seems it is in some sense necessary, although it also seems to be something that was contingent in the past. A way this might be explained is to say that it is not possible for any potency to have both come into act and not come into act. So if Washington was the first president (and he was) this is necessary de dicto (although not de re, since president is not predicated of Washington per se). — Count Timothy von Icarus
This mixes a few different notions of necessity. First, it is not a necessary fact that George Washington was your first president (Assuming you are 'Mercan?). We can stipulate a possible worlds in which he just sold apples. But you add "become", and here we can use accessibility. We can stipulate that from any world in which Washington became your first president, only those worlds in which he was the first president are accessible - we stipulate a rule of accessibility. If we do this then it follows that from that world, all accessible worlds have Washington as your first president - for those worlds, necessarily, Washington was your first president. Doing this puts limitations on the worlds that are under consideration - as it should. One of those is that in no world in which he was your first president, could he not be your first president. This should be obvious from considerations of consistency... And it is not true in every possible world, since that would be a different stipulation.
All this by way of showing how possible world semantics sets out what is problematic with
If "George Washington was the first US President" is true, and it is not possible for it to become false, it is in a sense necessary. — Count Timothy von Icarus
It's down to accessibility.
Nothing here so far involves essences.
Why must physical things be the only things to be rigidly designated? — schopenhauer1
They need not be. Anything that can be given a proper name can be rigidly designated. Kinds, such as gold or H₂O, can also be rigidly designated. But again, while causality may be the answer to how it is that a name refers to an individual, once that link is established, the causal chain becomes unnecessary. So Hesperus = Phosphorus even though the casual chains to their baptism differ.
Well, you could follow Quine and try to get rid of proper names... — Count Timothy von Icarus
But the problem then is that you have thrown the babe of rigid designation out with the bathwater of explaining reference.
Sheer "dubbing" runs into the absurdities of the "very same Socrates" who is alternatively Socrates, a fish, a coffee mug, Plato, a patch on my tire, or Donald Trump, in which case we might be perplexed as to how these can ever be "the very same" individual. — Count Timothy von Icarus
If someone were to misuse a term in this way, wouldn't that be apparent? Sure, someone could use "Socrates" to refer to some fish, but it would quickly become apparent that they were talking about something other than the philosopher.
Doesn't "Deer" man whatever we choose it to? Note the collective "we".
Indeed, but what is this internal coherence? — schopenhauer1
Very much, yep. Essence remains unexplained, apart from the occasional hand wave to "x=x". So the best explanation we have is still from Kripke.