Common nouns like "planet" might work in the same sort of way as proper nouns like "Michael" – the only difference is that one is plural and the other is singular. — Michael

This isn't really clear, especially with your hedging word "might" thrown in there. "Michael" is not descriptive, but it's just a random group of letters assigned to you as an identifier. "Planet" is a descriptive term, indicating that the item identified has certain qualities. It makes sense to say England is not a planet. It means that England lacks the characteristics of a planet. On the other hand, if you told me that you were Michael and I told you that I've spoken to you long enough to know you are not a Michael, you might be curious as to what I meant, as if there were something required in your personality or constitution to be a Michael.

You seem to want to avoid categorization of objects for some reason. If every object in a group has certain consistent characteristics, why can't I offer a single word (like "planet") to describe them? If later I figure out that I had miscatagorized a particular object, why would it be wrong to then remove it from that bucket?

Anyway, tell me why you want to go to such mental gymnastics here to avoid the straightforward position I've taken? Is there something deeper here I'm missing, as if you've got to go down your twisting road to avoid some other problem?

And Hanover isn't a German city. Hannover is. I missed the train in Hannover once. I just got on a different train that I didn't have a ticket for. I thought the Germans would care, but I explained to the train guy who looks at your ticket what happened, and he didn't care. They were weirdly flexible, very unGerman like. Maybe he stopped being "German" that day, sort of like Pluto stopped being a "planet" that other day.

If every object in a group has certain consistent characteristics, why can't I offer a single word (like "planet") to describe them? — Hanover

I'm not saying you can't. I'm saying that it doesn't then follow that being a planet is reducible to these consistent characteristics. These consistent characteristics might simply be contingent influences on our decision to impose the planet-identity on these things.

Furthermore, there might not be any consistent characteristics. As Wittgenstein said "How should we explain to someone what a game is? If we don't have a common thread running through everything we call a 'game' it seems very chaotic! How on earth do we teach people to use this term 'game'?
I imagine that we should describe games to him, and we might add: "This and similar things are called 'games'".

Trying to describe being a game by listing some set of material characteristics is a mistaken endeavour. You have to address our use of the word "game".

"Michael" is not descriptive, but it's just a random group of letters assigned to you as an identifier. "Planet" is a descriptive term, indicating that the item identified has certain qualities.

That's the notion I'm questioning. It's problematic, as shown with the example of games, and also of planets (the point of this discussion).

I'm saying that it doesn't then follow that being a planet is reducible to these consistent characteristics — Michael

There is something similar between the various objects. That is, objects A, B, and C all orbit the sun (for example). As such, we put A, B, and C in bucket X, and then we name bucket X "planet." If we realize that B doesn't orbit the sun, we remove it from bucket X.

These consistent characteristics might simply be contingent influences on our decision to impose the planet-identity on these things. — Michael

Sure, but you're just pointing out the consequences of an equivocation fallacy. We today call bucket X "Planet" whereas tomorrow we call bucket Y "Planet" and so to say that B is Planet today doesn't mean it's a Planet tomorrow because we've now redefined "Planet." I see none of this as a problem as long as we remain consistent in our terms over time.

What I'm saying is that Pluto was never a planet as long as planet has been defined the same way over time. Of course, if we've changed our definition of planet, then we're not talking about the same thing at all, in which case our problem is lack of clarity and nothing else.

Furthermore, there might not be any consistent characteristics. — Michael

This is nonsense really. There may not be anything similar in the objects we call planets? Then why do I notice all these similarities?

I really am not concerned that I can't itemize with specificity what it means to be a boat, for example, as I truly have no problem whatsoever distinguishing boats from houseplants and the like.

That's the notion I'm questioning. It's problematic, as shown with the example of games, and also of planets (the point of this discussion). — Michael

The problem doesn't appear to be in anything I've said, but it appears to be in what Wittgenstein said.

There is something similar between the various objects. That is, objects A, B, and C all orbit the sun (for example). As such, we put A, B, and C in bucket X, and then we name bucket X "planet." If we realize that B doesn't orbit the sun, we remove it from bucket X. — Hanover

So you're saying that to be a planet is to belong in bucket X and I'm saying that to be a planet is to belong in whichever bucket we name "planet".

Sure, but you're just pointing out the consequences of an equivocation fallacy. We today call bucket X "Planet" whereas tomorrow we call bucket Y "Planet" and so to say that B is Planet today doesn't mean it's a Planet tomorrow because we've now redefined "Planet." I see none of this as a problem as long as we remain consistent in our terms over time.

And my point is that being a planet is an identity that changes as our use of the word "planet" changes rather than an identity that's forever fixed to things in bucket X.

This is nonsense really. There may not be anything similar in the objects we call planets? Then why do I notice all these similarities?

I'm not saying that nothing is similar in the objects we call "planets". I'm saying that it might be that there isn't anything that all things named by some common noun have in common. What is the thing that all (and only) games have in common (the thing that determines whether or not a thing is a game)?

The problem doesn't appear to be in anything I've said, but it appears to be in what Wittgenstein said.

I disagree. I think Wittgenstein was right. It's nonsense to look for some material characteristic that is the "essence" of being a game. All we can do is look to how we use the word "game". There is a family resemblance of material characteristics that influence our language-use, but being a game isn't reducible to these characteristics (such that if our use of the word "game" changed then being a game wouldn't change).

Your initial example did seem to treat Pluto as a question of it characteristics rather than our category. Pluto(1) was implied to be different than Pluto(2) in terms of the object of Pluto, even though the characteristic that resulted in Pluto's reclassification wasn't new.

I'd say there was only one Pluto (object) and then our categorising of Pluto(1) and our categorising of Pluto (2).

The Wittgenstein point is this disagreement is meaningless because we are using different languages. To say Pluto is a planet uses a different category or language than saying it's not. In a more general sense of "planet," Pluto does qualify. Under the more specific version defined recently, Pluto does not qualify. Both categories are truthful. All we can do squabble about is which language we ought to use. It doesn't affect Pluto or the meaning of Pluto either way. If we are arguing over it, all we are doing is trying to get people to use one language over another.

So you're saying that to be a planet is to belong in bucket X and I'm saying that to be a planet is to belong in whichever bucket we name "planet". — Michael

This really is just evasive and not even responsive. We must assume there is some object out there that we've identified as Pluto and there is another object we've identified as Neptune and so on. That these objects might behave similarly is a metaphysical fact. If we note this similarity and name it "Planet," then that's what it is and all objects that behave in that manner fall into that class. If we put hats into the planet bucket, we've not made hats planets, we've made them "planets."

And my point is that being a planet is an identity that changes as our use of the word "planet" changes rather than an identity that's forever fixed to things in bucket X. — Michael

A planet is a thing in the sky. Pluto is "pluto" until we change the name.

I'm not saying that nothing is similar in the objects we call "planets". I'm saying that it might be that there isn't anything that all things named by some common noun have in common. What is the thing that all (and only) games have in common (the thing that determines whether or not a thing is a game)? — Michael

Ok, so if I have a blue lollipop and a blue chair, you're saying that they both might not be blue but that we've only named them both that way and when we rename them "green," they're no longer blue?

If no, please clarify. If yes, that's stupid.

I disagree. I think Wittgenstein was right. It's nonsense to look for some material characteristic that is the "essence" of being a game. All we can do is look to how we use the word "game". There is a family resemblance of material characteristics that influence our language-use, but being a game isn't reducible to these characteristics (such that if our use of the word "game" changed then being a game wouldn't change). — Michael

I don't think I've argued essentialism, and I don't think that any of what you say here affects my position. I agree there isn't some single component that can be identified that makes a chair a chair that could be sprinkled on a hat to make it a chair. There are likely a variety of things that make a chair a chair, some of which some chairs may have and some others don't. Perhaps it's a list of 100 criteria and if 40 are satisfied, it's a chair. Regardless, if the same chair criteria (or family resemblance or whatever) are satisfied at T-1 as at T-100, then it's still a chair. If we learn later that the object we were calling a chair at T-1 did not fit our criteria, it was not a chair at T-1.

There might be material facts that influence what sort of identities we impose on what sort of things, but the connection is merely contingent, not necessary. — Michael

Isn't that how language is meant to work? So it is the feature, not the bug.

A name is a symbol with no necessary connection to what it is meant to stand as a sign of. The word "pig" has no properties that are pig-like. So to call a pig "pig" is an arbitrary association.

But we then exploit that naming freedom in particular ways. Because we can thus give a name to anything at our whim, we can name those things that we believe are general, or are particular; that are fictional, or are real; that are contingent, or essential. Names can span the full gamut of possible ontic commitments by not being tied to any particular ontic commitments.

So the question of whether Pluto is a planet is understood as a language game with a particular ontic commitment. A planet is a real kind of object (or process) with nameable real properties - like being gravitationally spherical, and dominant in its orbit, big enough to clear a path of other contenders.

So yes, the act of naming is contingent in that clearly it we only bother to categorise the world in ways that reflect our epistemic interests. But then also, a major such interest is a comittment to ontic realism. We like to be able to classify the world into types of objects, and talk about the necessary qualities of these types, and the particularly significant instances of these types.

We develop a way of talking about reality that seems to get its reality right.

So while it can always be pointed out that names are arbitrary sounds coming out of our mouths, it is also the case that we are using this naming freedom to make a stronger ontic claim than it would otherwise be possible to make.

To call Pluto a planet is to assert it is a real object of that class, and so not some other class, like a moon, or an asteroid, or a planet-let. And in being real, that classification is open to being changed by empirical evidence. We can give names to a planet's essential qualities in terms of acts of measurement we might perform. It's all part of realism's particular language game.

So language organises naive experience into a structured place of ontic commitments. We can really develop a belief in real things because we also now know what it would be for them not to be real, but instead classified as fictions, ideas, faulty information, etc.

I'm not saying that nothing is similar in the objects we call "planets". I'm saying that it might be that there isn't anything that all things named by some common noun have in common. — Michael

And that's one reason semantic holism is attractive. Is that how you look at meaning?

Pluto didn't change. Our understanding of the universe changed as we gathered more information about it, and our language reflects our understanding of the universe, not the way the universe actually is. When we cease to learn more about the universe, only then will our understanding be complete and therefore our language will be complete as well.

And here's where it gets confusing.

I asked a layman about this yesterday and he said Pluto was never a planet. I asked, what about before 2006, when the consensus was that it was a planet, and I shit you not, he said that just because you call something a planet, doesn't mean it is one.

The fool!

This seems to speak to the distinction I wanted to make earlier between identity and identification. Being a planet does not seem to consist in any ontological identity as your and jamalrob's "Fool" would seem to be thinking. It's really not a case of being a planet at all, but of being identified and designated as a planet. So Pluto can be thought to be a planet according to one set of criteria and not to be a planet according to a different set. Pluto's identity does not consist in its being a planet, though, but in its status as a unique entity; because we cannot suddenly, by any reasonable criteria, decide that it is no longer an entity, whatever we might think it is or is not otherwise.