So the whole practice of referring becomes pointless. — Ludwig V

I do not see the problem; could you say it in another way?

No, that's not what contingent means. — Relativist

"Contingent" has varied meaning, it's quite ambiguous. I dismiss determinism, fatalism, and necessitarianism as fundamentally incompatible with our experience.

I perceive that the sun is shining. In my actual world the sun is shining.

I imagine a possible world in which the sun is not shining. It is possible that there is an actual world where the sun is not shining.

Actual worlds may exist or possibly exist. — RussellA

As I explained, that renders "actual" as meaningless. By "meaningless" I mean you could give it any meaning you want, but you haven't so it has no meaning. The world you perceive is "actual". The world you imagine is "actual". You could imagine anything, and that could be said to be "actual". What does "actual" mean? It doesn't mean to be imagined, because what you perceive is actual as well. It isn't that someone, not necessarily, you is perceiving it, because the imaginary ones are actual.

What meaning does "actual" have here? You could remove it from your example without changing the meaning of anything. "I perceive that the sun is shining. In my world the sun is shining." "I imagine a possible world in which the sun is not shining. It is possible that there is a world where the sun is not shining." See, "actual" does absolutely nothing in your usage.

In standard modal logic there is exactly one actual world. — Banno

This states very clearly and precisely, in a nutshell, the significant and substantial problem with possible worlds semantics. We must deny what you yourself acknowledged as the very real and important difference, between the "actual world" of ontology, and the "actual world" of modal logic. To avoid the fallacy of equivocation, there must be "exactly one actual world". The glaring problem though, is that "actual world" is assigned to the modal model, not the ontological world, plunging modal logic deep into Idealism.

(ii) its designated “actual world” is in fact the actual world, — SEP

Just a note, I've bowed out of the above discussion, but when Banno is ready to move on, I'm all in.

Well, you/Kripke have your reasons for saying that, I suppose. But it is clear that whatever "water" means is not based on that information. — Ludwig V

What does “water” mean? "Water" means different things to different people. To a scientist, "water" is necessarily H2O. To me, "water" is necessarily wet, in that if not wet it cannot be water. To a linguist, “water” is necessarily a noun. There is no one meaning of “water”, though each meaning is necessary within its own context.
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Again, perhaps so. But it follows that, whoever is called Aristotle is not necessarily the philosopher that we know and love. — Ludwig V

You love Aristotle for his philosophy. But instead of being born in Stagira, he could have been born in Athens and grown up to be a carpenter. So do you love Aristotle because of who he was or what he did?

What meaning does "actual" have here? You could remove it from your example without changing the meaning of anything. — Metaphysician Undercover

The words actual and possible are still needed.

In conversation, I might say “the sun might not be shining”, but would be confusing to a listener as it lacks context. It would be better to say “it is possible that the sun might not be shining”, as this does infer a context.

Similarly, my saying “the sun is shining” lacks context. It would be better to say “the sun is actually shining”.

The words "possible" and "actual" add context.

I do not think "air" is a rigid designator, and so I am happy to not designate any of the components, whether a majority component or not, as the necessary referent of the term "air." — NotAristotle

Wow, quite an admission. I guess you are saying that when it comes to these general, vague terms like "water" or "air", we have either two choices, one, say possible worlds semantics/rigid designators don't apply, or we can just remove the vagueness and just say "water" means "H2O".

when it so refers it will be the case that necessarily water is H2O as a result of the identity between the stuff and what is referred to by the term in that context. — NotAristotle

If you are indicating that these terms are interchangeable, this is wrong. You would think that if one is saying water is identical to H2O that they would be interchangeable. But that is not the case. For example, can you say that if you had one molecule of water you had one water? No, the term "water" when used in science refers to a collection of H2O molecules that under particular temperature and pressure conditions exhibit the macroscopic properties we typically call a "liquid." But guess what, under others conditions this collection of H2O molecule would not be called "water" anymore, but "steam" or "vapor", and under other conditions you would call it "ice".

So, what is all of this logic posturing by saying "water is H2O"is a posteriori necessary truth to achieve in the realm of science? To make prescriptive linguistic corrections like "Hey scientist, you forgot what Kripke said about "water is H2O", when you call that collection of H2O molecules "steam" you are wrong, please correct yourself and call it "water".

But you said that the possible worlds are actual, so you have no use for actual, regardless of context. The world you perceive is actual, and the possible worlds you imagine are all actual. "Actual" is meaningless. There is an implied difference between the perceived world and the imaginary worlds, but both those categories are actual, so "actual" serves no purpose.

just say "water" means "H2O" — Richard B

Why is that controversial?

the term "water" when used in science refers to a collection of H2O molecules that under particular temperature and pressure conditions exhibit the macroscopic properties we typically call a "liquid." — Richard B

Okay then, "water" is interchangeable with...

a collection of H2O molecules that under particular temperature and pressure conditions exhibit the macroscopic properties we typically call a "liquid." — Richard B

The words actual and possible are still needed.

In conversation, I might say “the sun might not be shining”, but would be confusing to a listener as it lacks context. It would be better to say “it is possible that the sun might not be shining”, as this does infer a context.

Similarly, my saying “the sun is shining” lacks context. It would be better to say “the sun is actually shining”.

The words "possible" and "actual" add context. — RussellA

The modality is equally relevant. Your modality is epistemic: given the facts available to you, it is (epistemically) possible the sun is shining.

But if the sun is actually shining, then although you don't know this fact, it is physically, metaphysically, and logically impossible for the sun to not be shining at that point of time. (Law of noncontradiction).

Yet another issue: is the sun shining at that point of time a contingent fact, or a necessary fact?

There is an implied difference between the perceived world and the imaginary worlds, but both those categories are actual, so "actual" serves no purpose. — Metaphysician Undercover

I can imagine a possible world where aliens live. This imagined possible world may in fact be an actual world.

I agree that if my perceived world was “actual” and all imagined possible worlds were “actual”, then the word “actual “ would be redundant.

However, if my perceived world was “actual” and some imagined possible worlds were “actual”, then the word "actual “ would not be redundant (because some imagined possible worlds would not in fact be “actual”.)

The difference is in the quantifiers all and some.

This imagined possible world may in fact be an actual world. — RussellA

The point, though was that all the possible worlds are actual worlds. If we say "possible" that means "may" be. But Lewis' interpretation appears to be that each possible world "is" an actual world. That's what we were discussing, all the possible worlds are actual worlds.