I think this radically misunderstands what thought experiments are for. As I see it, the job of philosophy is to clear up our own conceptual confusions; that's not the sort of thing that ever could conflict with science!
(EDIT: I mean that it shouldn't conflict with science; if you do your philosophy wrong then you might end up conflicting.)
Besides, Putnam's thought experiment can be easily tweaked to get around that problem: suppose that on Twin Earth cats are in fact very sophisticated cat-imitating robots. Then a similar conclusion follows about the meaning of "cat". The point is that if X had in fact been Y, where Y is the same as X in all the respects which we use to pick out X, then words which currently refer to X would refer to Y in that situation. I think Putnam even specifies that we are to imagine that XYZ behaves chemically the same as H2O. Sure, that couldn't happen in our world; but the laws of physics might have turned out differently, and we ought to be able to conceptually deal with possibilities like this.
Just to be clear, I think that analytic philosophers often should have been more humble when they barged in and started telling scientist how confused they were. Fodor's critique of NS would again be my go-to example of that.
Dennett states this point in typically strong terms in his review of Fodor's argument:
I cannot forebear noting, on a rather more serious note, that such ostentatiously unresearched ridicule as Fodor heaps on Darwinians here is both very rude and very risky to one’s reputation. (Remember Mary Midgley’s notoriously ignorant and arrogant review of The Selfish Gene? Fodor is vying to supplant her as World Champion in the Philosophers’ Self- inflicted Wound Competition.) Before other philosophers countenance it they might want to bear in mind that the reaction of most biologists to this sort of performance is apt to be–at best: “Well, we needn’t bother paying any attention to him. He’s just one of those philosophers playing games with words.” It may be fun, but it contributes to the disrespect that many non- philosophers have for our so-called discipline.
As I see it, the job of philosophy is to clear up our own conceptual confusions; that's not the sort of thing that ever could conflict with science!
It certainly can, if the job is done badly.
Agreed that Grisdale's argument isn't very good, I have a hard time taking Putnam's argument seriously, or even the whole context in which he presented his thought experiment. Like a lot of philosophy, it reminds me of a bunch of maths noobs arguing long and futilely in a not-even-wrong manner over whether 0.999...=1.
We on Earth use "water" to refer to a certain substance; those on Twin Earth use "water" to refer to a different substance with many of the same properties; our scientists and theirs meet with samples of the respective substances, discover their constitutions are actually diffferent, and henceforth change their terminology to make it clear, when it needs to be, which of the two substances is being referred to in any particular case.
There is no problem here to solve.
Well, sure, you can do philosophy wrong!
It sounds to me that you're expecting something from Putnam's argument that he isn't trying to give you. He's trying to clarify what's going on when we talk about words having "meaning". His conclusion is that the "meaning", insofar as it involves "referring" to something, depends on stuff outside the mind of the speaker. That may seem obvious in retrospect, but it's pretty tempting to think otherwise: as competent users of a language, we tend to feel like we know all there is to know about the meanings of our own words! That's the sort of position that Putnam is attacking: a position about that mysterious word "meaning".
EDIT: to clarify, I'm not necessarily in total agreement with Putnam, I just don't think that this is the way to refute him!
I've always thought this argument of Putnam's was dead wrong. It is about the most blatant and explicit instance of the Mind Projection Fallacy I know.
The real problem for Putnam is not his theory of chemistry; it is his theory of language. Like so many before and after him, Putnam thinks of meaning as being a kind of correspondence between words and either things or concepts; and in this paper he tries to show that the correspondence is to things rather than concepts. The error is in the assumption that words (and languages) have a sufficiently abstract existence to participate in such correspondences in the first place. (We can of course draw any correspondence we like, but it need not represent any objective fact about the territory.)
This is insufficiently reductionist. Language is nothing more than the human superpower of vibratory telepathy. If you say the word "chair", this physical action of yours causes a certain pattern of neurons to be stimulated in my brain, which bears a similarity relationship to a pattern of neurons in your brain. For philosophical purposes, there is no fact of the matter about whether the pattern of neurons being stimulated in my brain is &...
Putnam perhaps chose poor examples, but his thought-experiment works under any situation where we have limited knowledge.
Instead of Twin Earth, say that I have a jar of clear liquid on my desk. Working off of just that information (and the information that much of the clear liquid that humans keep around are water) people start calling the thing on my desk a "Jar of Water." That is, until someone knocks it over and it starts to eat through the material on my desk: obviously, that wasn't water.
Putnam doesn't think that XYZ will look like water in ...
I'm not sure that showing that XYZ can't make something water-like is any more helpful than just pointing out that there isn't actually a Twin Earth. Yes, it was supposed to be a counterfactual thought experiment. Oh noes, the counterfactual doesn't actually obtain!
And showing that particular chemical compounds don't make water, doesn't entail that there is no XYZ that makes water.
And as army1987 pointed out, it could have been "cat" instead of "water".
I'm going to agree with those saying that Thagard is missing the point of Putnam's thought experiment. Below, I will pick on Thagard's claim that Grisdale has refuted Putnam's thought experiment. For anyone interested, Putnam's 1975 article "The Meaning of "Meaning"", and Grisdale's thesis are both available as PDFs.
Thagard says that Grisdale has refuted Putnam's thought experiment. What would it mean to refute a thought experiment? I would have guessed that Thagard meant the conclusion or lesson drawn from the thought experiment is...
What a silly thought experiment. The fact that two people use one word to refer to two different things (which superficially appear similar) doesn't mean anything except that the language is imperfect.
Case in point: Uses of the word "love".
Pointing out that biochemistry couldn't be the same if water was different sounds like deliberately missing the point of Putnam's experiment. Suppose a planet like Earth, but where most people are left-handed, have their heart in the right-hand side of their body, wear wedding rings on their right hand, most live in the hemisphere where shadows move counterclockwise, most screws are left-handed, conservative political parties traditionally sit in the left-hand side of assemblies, etc., etc., and they speak a language identical to English except that left m...
It depends on your thought experiment - mathematics can be categorised as a form of thought experimentation, and it's generally helpful.
Thought experiments show you the consequences of your starting axioms. If your axioms are vague, or slightly wrong in some way, you can end up with completely ridiculous conclusions. If you are in a position to recognise that the result is ridiculous, this can help. It can help you to understand what your ideas mean.
On the other hand, it sometimes still isn't that helpful. For example, one might argue that an object can't ...
I think many of the other commenters have done an admirable job defending Putnam's usage of thought experiments, so I don't feel a need to address that.
However, there also seems to be some confusion about Putnam's conclusion that "meaning ain't in the head." It seems to me that this confusion can be resolved by disambiguating the meaning of 'meaning'. 'Meaning' can refer to either the extension (i.e. referent) of a concept or its intension (a function from the context and circumstance of a concept's usage to its extension). The extension clearly ...
Twin Earth is impossible in this universe. A universe could exist just like ours, except that water is made of a compound of xenon, yttrium, and zing (XeYZn). Furthermore, the laws of physics are such that this chemical acts like water does in ours, and everything else acts just like water in ours. The laws would have to be pretty bizarre, but they could exist.
This quote misunderstands the zombie thought experiment as used by Chalmers. Chalmers actually thinks zombies are impossible given the laws that actually govern the universe, and possible only in the sense it's possible the universe could have had different laws (or so many people would claim.)
I'm not as sure about Putnam's views, but I suspect he would make an analogous claim, that his thought experiment only requires Twin Earth to be possible in a very broad sense of possibility.
Putnam's flaw is to try to prescribe how language works. Putnam is like, language works like X because it has to, ignoring that we create language and can choose how it works. I'd agree with the suggestion further up that the typical mind fallacy is at work here.
A similar point is that a lot of bad theories historically are the result of trying to explain something that should just be taken as an irreducible primary. Aristotle tried to explain "motion" by means of the "unmoved mover", Newton was treated skeptically because his theory didn't explain why things continued to move, Lavoisier's theory of oxygen I think was treated similarly contra phlogiston.
I think something is missing here. Suppose that water has some unknown property Y that may allow us to do Z. This very statement requires that water somehow refers to object in the real world, so that we would be interested in experimenting with the water in the real world instead of doing some introspection into our internal notion of 'water'. We want our internal model of water to match something that is only fully defined externally.
Other example, if water is the only liquid we know, we may have combined notions of 'liquid' and 'water', but as we explo...
I don't think there is anything special about consciousness. "Consciousness" is what any intelligence feels from the inside, just as qualia are what sense perceptions feel like from the inside.
Putnam perhaps chose poor examples, but his thought-experiment works under any situation where we have limited knowledge.
Instead of Twin Earth, say that I have a jar of clear liquid on my desk. Working off of just that information (and the information that much of the clear liquid that humans keep around are water) people start calling the thing on my desk a "Jar of Water." That is, until someone knocks it over and it starts to eat through the material on my desk: obviously, that wasn't water.
Putnam doesn't think that XYZ will look like water in every circumstance: his thought-experiment includes the idea that we can distinguish between XYZ and water with, say, an electron microscope. So obviously there are some properties of XYZ that are not the same as water, or else they really would look the same under every possible circumstance.
The difference (which is where some philosophers make the mistake) is when you assume that the "thought-experiment" stuff looks like the "real" stuff in every possible circumstance. If Putnam had said that the difference between H2O and XYZ was purely ephiphenomenal or something like that, he'd be obviously wrong. For instance, if we looked at XYZ and it "fooled" us into thinking it was H2O (say, if we broke apart XYZ and got a 2:1 ration of oxygen to hydrogen and no other parts) then Putnam's argument wouldn't hold. (This is where p-zombies fail: it is stipulated that there is no experiment that can tell the difference.)
Putnam's main point was that we can be mistaken about what a thing is. Moreover, that when we can have two things (call them A and B) that we think are of the same type that we can not only be mistaken that A and B are of the same type, but that A could fit the type and B might not.
If this seems incredibly basic... it is. People make a big deal about it because prior to Putnam (and sometimes afterward) philosophers were saying crazy things like "the meanings in our heads don't have to refer to anything in the world," which essentially translates to "I can make a word mean anything I want!"
I agree with this to the extent that we shouldn't make the mistake that just because we have a model of something in our head means that our model corresponds to the real world. It's even stickier, because when a model doesn't conform we often keep the words around because they can be useful descriptions of the new thing we've fround. That can create confusion, especially during a period of transition. (Imagine someone saying that "Water cannot be H2O, because it is necessarily an Aristotelian element.") But thought experiments are very, very useful since all a "thought experiment" really is, is when you use the information already in your head and say, "Given what I already know, what do I think would happen in this circumstance?"
Putnam's main point was that we can be mistaken about what a thing is. Moreover, that when we can have two things (call them A and B) that we think are of the same type that we can not only be mistaken that A and B are of the same type, but that A could fit the type and B might not.
I think he's making a slightly different point. His point is that the reference of a term, which determines whether, say, the setence "Water is H2O" is true or not, depends on the environment in which that term came to be used. And this could be true even for speake...
Thagard (2012) contains a nicely compact passage on thought experiments: