I didn't mean identity in that sense. I meant in the sense of being of a certain kind.

OK, so I am saying being of a certain kind is a matter of identification, and not a matter of identity. What category we place things in has no effect on the things. Being a planet is not a matter of identity, but identification, whereas being a unique entity (whatever kind of entity that might be) is a matter of identity. Looked at this way, the apparent puzzle dissolves, I think.

That doesn't really address the issue though. The issue is that if Pluto isn't a planet then either it was never a planet or being a planet cannot be reduced to having certain material characteristics.

Of course, if like TGW you want to say that Pluto is still a planet then the problem doesn't arise.

On the contrary, I would say that if Pluto isn't a planet then either it was never a Planet, or being-a-planet can be reduced to having certain material characteristics. I think the former alternative is incoherent, so I would go for the latter.

What the word 'horse' means depends on how the word 'horse' is used. This is not the same as saying that what it is to be a horse depends on how the word 'horse' is used, which is what you're claiming. You seem to think these two are the same, which is a confusion, whether or not you'd still hold the view once you differentiated them properly.

In fact I find your views kind of fascinating, almost to the extent that I would give them to undergraduates as essay prompts as examples of linguistic confusions for them to untangle in the Wittgensteinian mode. — The Great Whatever

I look at it like this:

Why is "triangles are three-sided shapes" true? Because "triangle" and "three-sided shape" mean the same thing. Why do "triangle" and "three-sided shape" mean the same thing? Because we use "triangle" and "three-sided shape" in the same sort of way. Therefore if we used "triangle" and "three-sided shape" in incompatible ways then they would mean different things, and so "triangles are three sides shapes" would be false. The way we use the word "triangle" influences the truth-value of the sentence "triangles are three-sided shapes".

And so by the same token, the way we use the word "planet" influences the truth-value of the sentence "Pluto is a planet".

The problem with this analogy is that planets are entities with much more complex sets of properties than triangles, so the fact that it seems semantically straightforward in the case of the latter does not justify any demand or assertion that the case of the former must be similarly straightforward.

You've misunderstood.

If Pluto isn't a planet and if being a planet can be reduced to having certain material characteristics and if the material characteristics of Pluto haven't changed then Pluto was never a planet.

If Pluto isn't a planet and if Pluto was a planet and if the material characteristics of Pluto haven't changed then being a planet cannot be reduced to having certain material characteristics.

So if we accept that Pluto isn't a planet and if we accept that the material characteristics of Pluto haven't changed then either a) being a planet can be reduced to having certain material characteristics and so Pluto was never a planet, or b) Pluto was a planet and so being a planet cannot be reduced to having certain material characteristics.

One of the following must be false:

1. Pluto isn't a planet
2. Pluto was a planet
3. Being a planet can be reduced to having certain material characteristics
4. The material characteristics of Pluto haven't changed

If we used the word "planet" to refer to stoves then the word "planet" would mean "an apparatus for cooking or heating that operates by burning fuel or using electricity", and so "Pluto is a planet" would be false.

I don't think I've misunderstood at all. It is not simply a matter of being a planet; it is a matter of being considered to be a planet. If the word 'planet' comes to preside over a different set of characteristics than it did formerly, then Pluto was indeed never a Planet under the new definition, but was and still is a Planet under the old different definition. There is no contradiction in this; either way Pluto will never cease to be an entity, so its identity is safe.

In the case of triangles it is not conceivable that the set of characteristics that define them could ever change; so the analogy is simply not a good one.

Why is "triangles are three-sided shapes" true? Because "triangle" and "three-sided shape" mean the same thing. Why do "triangle" and "three-sided shape" mean the same thing? Because we use "triangle" and "three-sided shape" in the same sort of way. — Michael

Agreed.

Therefore if we used "triangle" and "three-sided shape" in incompatible ways then they would mean different things, and so "triangles are three sides shapes" would be false. — Michael

Correct.

The way we use the word "triangle" influences the truth-value of the sentence "triangles are three-sided shapes". — Michael

Yes.

And so by the same token, the way we use the word "planet" influences the truth-value of the sentence "Pluto is a planet". — Michael

But from this it does not follow that the way we use the word 'planet' influences which individuals are planets. Your conclusion simply does not follow from your premises, which is what I am trying to get you to see. Whether you are ultimately right or not, which I still think you are not, your current position rests on a conflation and a misunderstanding, and your position can't be investigated until you understand that.

For me it's getting a little far from common usage to say that Pluto was not a planet and now is.

I think a more accurate rendering of how the words are used is to say:
1. When people referred to Pluto as a planet (not a planet) in 1980 they were correct (incorrect); and
2. When people referred to Pluto as a planet (not a planet) in 2015 they were incorrect (correct).

What has changed is simply what the wider linguistic community - in this case heavily under the influence of public announcements by astronomers - considers to be correct use of the word 'planet'.

The key point is that, in assessing a statement for correctness, we often need to know who is saying it, and where and when. Statements don't exist outside of space and time. Context is (almost) everything.

Given that framework, it's only if one wants to take an essentialist or Kripkean view that there is some 'essential nature' of a planet (or a rigid designator) that gets dilemmatised.

Why is "triangles are three-sided shapes" true? Because "triangle" and "three-sided shape" mean the same thing. Why do "triangle" and "three-sided shape" mean the same thing? Because we use "triangle" and "three-sided shape" in the same sort of way. Therefore if we used "triangle" and "three-sided shape" in incompatible ways then they would mean different things, and so "triangles are three sides shapes" would be false. The way we use the word "triangle" influences the truth-value of the sentence "triangles are three-sided shapes".

And so by the same token, the way we use the word "planet" influences the truth-value of the sentence "Pluto is a planet". — Michael

There is another significant and problematic difference that is fatal for your analogy and argument here. 'Triangle' means "three angled shape" and an enclosed three angled shape must have three sides. So, by logical extension 'triangle' must mean 'three-sided shape'; it is a non-arbitrary meaning due to the concepts that are joined together in the word 'triangle'. The same kind of semantic conditions do not obtain in the case of 'planet'.

1. When people referred to Pluto as a planet (not a planet) in 1980 they were correct (incorrect); and
2. When people referred to Pluto as a planet (not a planet) in 2015 they were incorrect (correct). — andrewk

The question, though, is whether or not it is correct now to say that Pluto was a planet. If it was a planet then being a planet cannot be reduced to having certain material characteristics and if being a planet can be reduced to having certain material characteristics then Pluto wasn't a planet.

Of the 4 statements I accept 1, 2, and 4, and so I must reject 3.

The question, though, is whether or not is correct now to say that Pluto was a planet. — Michael

It depends, as (nearly) always, on context. That statement actually has two time inputs, but they are hidden, making the statement ambiguous. Let us define a predicate N with four arguments. N stands for 'noun' - common noun in fact.

N(x,t1,n,d) is true iff object x at time t1 qualified to be described as noun (category) n according to definition d. But definitions change over time and place, so d actually is itself a function of two arguments: time t2 and location l. Let's use a function def of three arguments such that def(u,v,w) refers to the definition of word u that was generally accepted in the vicinity of v at time w.

So we write our applied predicate more fully as
N(x,t1,n,def(n,t2,l))
In words:
'x was at time t1 an n according to the definition of n that was generally accepted at time t2 in the vicinity of l.
In the Pluto planet case we substitute 'Pluto' for x and 'planet' for n so the expression is, in precise form:
N(Pluto, t1,planet,def(planet,t2,l))
and in words:
'Pluto was at time t1 a planet according to the definition of planet that was generally accepted at time t2 in the vicinity of l.

A statement like 'Pluto was a planet in 1980' is neither correct nor incorrect. It is simply ambiguous speech, because it has not specified what definition of planet is to be applied. Two time coordinates are required in order to avoid ambiguity. Only one has been supplied, and it is not clear whether the 1980 is supposed to serve as t1, t2 or both.

In ordinary speech we usually do not supply all the necessary arguments to the implicit predicates and functions in our sentences, because they can be readily inferred by the context. But not infrequently, ambiguity arises because the context does not allow all the missing inputs to be uniquely inferred.

It's like when my partner says 'can you help me with this?'

The question, though, is whether or not is correct now to say that Pluto was a planet. — Michael

And the answer is that it is correct now to say that under the present definition of 'planet' it was, and is, not a planet, and that under the past definition of 'planet' it was, and is, a planet.

I think there is no significant philosophical problem here, and that you are merely confusing yourself with words.

So the question is; what is criterion X, and has Pluto ever met it? If criterion X is some set of material characteristics, and if Pluto has never had these material characteristics, then Pluto has never been a planet. — Michael

That would be correct. If Pluto = x, y, and z and a planet = x, y, z, and a, then Pluto was never a planet. We just thought it was because we didn't realize it lacked the "a" element.

I suppose there can be some ambiguity here which leads to confusion, but as long as we keep our terms clear, I don't see a problem. That is, if we define Planet in two different ways: (1) a common usage way, and (2) a scientifically prescribed way, then I can see where there is a problem, but that's just an equivocation fallacy. If in year -5 we called Pluto a planet, it was a planet insofar as definition #1 was met, but it was not a planet insofar as definition #2 was met. In year +5, we have changed our #1 definition to comport with the #2 definition, so we don't consider Pluto a planet either in the vernacular or in the scientifically prescribed way.

My father always thought himself to be an identical twin. There was never any genetic testing. If he had been tested, and it were determined he was a fraternal twin, then it would be accurate to say he was never an identical twin despite the fact that he previously considered himself to be. How's this controversial, and how's this different from the Pluto question?

To be a planet, then, is to be named a planet. — Michael

This conclusion is demonstrably absurd, so there must be an error in the reasoning leading up to it.

Is there a difference between being a planet and being called a planet? — Michael

Obviously.

There may well be more controversial aspects to this issue, but let's at least start with what we know.

I'm with TGW on this one, as, I recall, I have been in past discussions on this topic. He's talking a lot of sense in this discussion.

If Pluto was a planet, and nothing about Pluto has changed in such a way as to render it no longer a planet, then Pluto is still a planet.

If Pluto wasn't a planet, and nothing about Pluto has changed in such a way as to render it a planet, then Pluto is still not a planet.

If Pluto was a planet, and nothing about Pluto has changed in such a way as to render it no longer a planet, but a significant group of people have removed "Pluto" from the category "planet", then Pluto is still nonetheless a planet, despite it having been recategorised. For those within the group, it is appropriate to identify Pluto as a non-planet (even though Pluto is a planet).

I trivially disagree with TGW by going with the second option, because, somewhat arbitrarily, I adopt the current scientific classification, and so it follows that Pluto is not, and never was, a planet. It was merely considered as such for a significant period of time.

Was the morning star the evening star before it was known they were both Venus, which is a planet, and not a star? It's clear that "morning star" references something different than "evening star" in terms of when the object appears. And it's clear that it's a misnomer, as it's not a star at all.

So, we could say that Pluto(1), which was what we thought to be a planet, is different than Pluto(2), which we now don't consider to be a planet. Pluto(1) occurred from T1 to T100 and Pluto(2) is occurring from T101 to current day. Obviously, Pluto(1) and Pluto(2) are the same physical object, but the former occurred at an earlier time, so we, for whatever arbitrary reason, can classify it separately based upon its occurrence time if we want to.

Here's my question: what is the philosophical import of all this? I think I see the puzzle, but I don't see any far reaching implications here.

Here's my question: what is the philosophical import of all this? I think I see the puzzle, but I don't see any far reaching implications here. — Hanover

Neither do I. I don't think there are any, if you, me and tee-gee are correct (which we are).

If, on the other hand, Yaha- I mean Michael, is correct, then stoves became planets if you call 'em planets, because a triangle is a three-sided shape.

Therefore, Banno is a red cup.

I don't think there are any purely academic issues in philosophy. Questions like this have deep consequences in the way you view language, identity, and the question of realism. It's all connected, and if you have a basic error in reasoning here, it will infect every other issue you tackle, and lead to a lot of useless speculation and literature on a mistaken premise.

If Pluto was a planet, and nothing about Pluto has changed in such a way as to render it no longer a planet, then Pluto is still a planet.

If Pluto wasn't a planet, and nothing about Pluto has changed in such a way as to render it a planet, then Pluto is still not a planet. — Sapientia

Yes, I agree with this, since you are saying basically exactly what I said in my last post.

You are equivocating on what it means to be "philosophically significant"; of course if someone spends their time concerning themselves with issues that are of no philosophical significance the fact they do that may be of great consequence to their life and their interactions with others. If a whole culture does that, then....Only in that sense, such time-wasting may be said to be of ethical (and by extension philosophical) significance.

If, on the other hand, Yaha- I mean Michael, is correct, then stoves became planets if you call 'em planets, because a triangle is a three-sided shape. — Sapientia

Well, I can see where stoves will become "planets" if we call stoves "planets," but I can't see how a stove can become a planet. An object can't morph into another object based upon our classification, but an object can be reclassified however we want to do it.

Am I missing something? Can someone restate Yahadraes/Michael/Mr. Awesome's view?

Yes, I agree with this, since you are saying basically exactly what I said in my last post. — John

And someone somewhere no doubt said "basically exactly" what you and I both just said before we said it, but I'm glad you agree. I have probably already said more or less the same thing in one of the many past discussions on this topic, although I don't remember the one about horses.

Well, I can see where stoves will become "planets" if we call stoves "planets," but I can't see how a stove can become a planet. An object can't morph into another object based upon our classification, but an object can be reclassified however we want to do it.

Am I missing something? Can someone restate Yahadraes/Michael/Mr. Awesome's view? — Hanover

I'm a bit confused as well. I half-jokingly presented that view and ascribed it to Michael, but although he denies it, it does seem to be implied by some of his claims. It seems to be a case of wanting to have your cake and eat it. It's problematic to break down these important distinctions between classification and actuality, between what something is and what something is called.

Yes, no doubt they did! And I'm sure I also have made just this kind of point many times in the past. It's a fairly commonsensical point, I think.

The exchange in the thread about horses between Michael and TGW was even longer and sillier than the one here, if I remember. Like you, I thought TGW was making the more sense there.

It's not time wasting. You're not above it. It's a serious and interesting question and if you don't like it go somewhere else where your valuable time is better spent.

I don't think the question is "serious and interesting". The fact it can be answered so easily by common sense attests to that. Judging by your own responses I had thought you also thought that. Of course, that is only my opinion about what is philosophically interesting, everyone is free to spend their time however they like, and I would never presume to tell some one they are wasting their time, unless I believe their inquiry is based on a conceptual confusion or category error, such as in this case confusing identification with identity. Personally if I was wasting my time on such a category error or confusion I would be pleased to be set right about it, so that I could get on with more fruitful pursuits. But others are free to disagree and to continue to, as I see it at least, cling to their errors if they want to.

I don't think the question is "serious and interesting". The fact it can be answered so easily by common sense attests to that. — John

What's interesting about problems such as these is that they can indeed be answered by common sense, and are done so in many cases, at least initially; but then philosophy comes along and induces puzzlement, and it then becomes a superficial problem which can persist unless one snaps out of it and realises what they already knew in the first place.

Am I missing something? Can someone restate Yahadraes/Michael/Mr. Awesome's view? — Hanover

My view is that identity might be a linguistic/conceptual imposition, and not something that is to be simply reducible to having certain material characteristics. 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. 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.

So in saying "if everyone calls stoves 'planets' then stoves are planets" I'm not saying "if everyone calls stoves 'planets' then stoves are celestial bodies", just as in saying "if everyone calls you 'Hanover' then you are Hanover" I'm not saying "if everyone calls you 'Hanover' then you are a German city". It seems to me that the criticisms against my position have actually been against this misinterpretation (despite the fact that I've rejected such an interpretation multiple times).