The following is a thought experiment conjured by Hillary Putnam, professor emeritus and all-around influential philosopher at the thinkery known as “Harvard.”
Somewhere in the universe is a remote planet. It is like Earth with one important difference. It is the only place in the universe that has a very peculiar liquid. That liquid is transparent at room temperature, and is vital for biological chemistry on that planet. It freezes at 0 degrees C., and actually becomes less dense as it does so, unlike any other liquid with which the inhabitants of that world are acquainted. The stuff boils at 100 degrees C. It is composed of two parts of one element, and one of another. The inhabitants of this planet obviously drink and cook with the liquid, use it as a general purpose solvent, curse the stuff when it falls frozen in mass quantities during cold weather, fairly mucking up their driveways, highways and byways. It constitutes that world’s vast oceans, its rivers, lakes and, of course, clouds. Fish swim in the stuff...and...Well, you get the idea.
Why on Earth say this liquid is peculiar? It’s obvious we are talking about water here. Ah. But, that is where you would be wrong. The substance on this planet is not water. Sure, it has the macroscopic properties of water, but it isn’t water. It’s some other chemical combo. Putnam calls it ‘XYZ.’ But to preserve the two to one ratio in the chemical composition, let’s call it X2Y.
What is more, this planet is in all other respects just like Earth. At this very moment there is another shlub banging away at a keyboard in an ill-lit office, writing up this very thought experiment. As you, dear reader, are reading the intertubes result, there is another reader, your doppelganger (and no shlub) reading along, just as you are doing, a sort of Harpo Marx to your Groucho (or Lucille Ball if you remember that “I Love Lucy” episode), excepting of course, that your twin is in every respect like you, save his/her watery components.
In fact, the histories of our two worlds, Earth and Twin Earth (TE) are and will be identical.
Now, think about what is going on when we on Earth, and our doppelgangers on TE, think about and talk about water, or rather, the stuff we call “water.”
Imagine that a four year old is thinking about the water he has just jumped into. The pool is not heated, and he lives in Michigan. “Wow,” he thinks, “this water is cold!” So also thinks his doppelganger in Twin-Michigan on Twin Earth.
Suppose I think “Man, I’m thirsty. I sure could go for a glass of ice-water.” I will have, accompanying these words, a series of thoughts, images, even actions as I move to satisfy that desire. So also thinks my doppelganger.
Now, consider the Earth chemist sitting in his lab, conducting some experiment on dissolution rates of salt in water. He thinks “I’ll test the dissolution rate at 39.2 degrees Fahrenheit.” So also thinks the TE doppelganger.
Now, is there any discernable difference in the contents of each of these person’s thoughts? What can we say in answer to this question about case one? It would seem to be that from a phenomenological perspective, the answer is ‘no’. The kids have exactly similar thoughts about exactly similar sensations in exactly similar circumstances. The two kids are referring to a pool of liquid, the one they jumped into, using the word “water”.
Aside from the fact that one set of thoughts is being had by Earth kid, and the other is being had by TE kid, are there any other facts that would allow us to say that the thoughts they are having or the propositions they are expressing by using the same set of words, are in fact different thoughts or propositions? The answer is fairly clear according to Putnam: As we run through the ‘catalog’ of mental goings on and non-mental features that constitute or are involved with the thoughts of the two kids, there seems to be only one thing that stands out as difference making: The stuff the two kids refer to with the word “water” is different. So, we can say on that basis, that the propositions are indeed different. We can “individuate” them this way. Sticking to our restriction of ignoring place, and thinker, we can say that one thought or proposition is not the other, based upon this one difference.
The situation is analogous to the situation you might have if you just consider the content of a blog post which is being read at two different locations at the same time. Ignoring the fact that the thing is being read at two locations, using two different machines, and two different brains, and just focusing on the content, we would be forced to say that it is ‘the same post’ or the same ‘content’ or the same set of propositions being read. In a very real sense one and the same ‘thing’ is at two locations at the same time. Similarly, in our present case involving the kids, if you ignore not only place and person, but the things to which the word “water” refers, you will be hard pressed to individuate the thoughts in the two kids’ minds. Indeed, they will appear very like the blog posting, the very same thing at two different locations.
Now, consider the next case; myself and the glass of ice-water. I know a bit more than the kids. So does my doppelganger. I know that the word I use refers to collections of H2O. My doppelganger knows it refers to collections of X2Y. So, we find an easy way to ‘individuate’ our mental states based upon internal states, even if we ignore place and person. His thought is different than mine, because he knows it refers to X2Y, while I know mine refers to H2O. The words we use, and the thoughts or propositions they instantiate or communicate come to refer to these things because the two substances caused us to have the thoughts and concepts via some historical process or other. Something similar can be said about the two chemists.
So, at least in these latter two cases, what makes a thought the thought it in fact is, is something we can describe as internal to the thought, even if that internal stuff was acquired because one of the words actually referred to something outside the two minds (either me and twin me, or the two chemists).
On the other hand, in the kids case, what makes the two thoughts the thoughts they are, and what makes them non-identical is stuff that appears to simply be outside the noggins of the two kids. This puzzles Putnam, makes him uncomfortable. Why?
Presumably, what differentiates propositions from one another are their meanings. The constituents of propositions are simpler elements, usually we simply think of them as words, but they are the concepts behind the words, the things the words are intended to communicate or elicit in others.
Well, in these special cases (which are really not so special, but common) those meanings would appear to be partly constituted by things that are not mental at all, not internal to the user of the propositions or words. Somehow or another stuff in the inanimate world becomes part of the meaning of words, becomes part of the allegedly abstract entities we call ‘propositions’.
To use Putnam’s catch phrase; ‘meanings just aint in the head.’
Similar arguments have been made concerning proper names. Saul Kripke is famous for presenting something like this thought experiment with the proper names “Moses”, “Jonah” and “Gödel”. (someone tell me where that umlaut key is eh? *note* spell check supplied it! Since when does the word bank include names?)
Kripke tells the story of some obscure individual who really discovered the incompleteness theorem, and from whom Gödel stole that historic insight. He argues: If the name simply referred to, or meant “the discoverer of incompleteness” that name would refer, when used, to Mr. Lost in Obscurity, not Gödel.
Kripke has us run a thought experiment to back up this claim. We should ask ourselves to whom the name refers, when it is used in a college classroom? Does it refer to Kurt Gödel or Mr. Lost in Obscurity?
Kripke’s answer; It refers to Gödel, despite the fact that he really didn’t discover incompleteness. Interestingly, some psychologists have teamed up with philosophers to test these claims. They generally test college students, and have taken pains to test across cultures, to see if there are any noticeable deviations from Kripke’s claims about what “we” say in such cases. There are a noticeably larger number of individuals of Asian descent (meaning Japan, India and other areas) that will declare beliefs counter to Kripke’s prediction, saying that the name Gödel does indeed refer to Mr. Lost in Obscurity. Tests have yet to be run on natural kind terms like water, but, no doubt are in the works. Experimental philosophy. Cool stuff.
So, what does the result show us about how ‘we’ treat proper names? Answering for this particular name, Kripke says: Even though we associate the description with the name, and through the name, we associate it with the man Kurt Gödel, we do not treat the description and name as synonyms. How, then does the name come to refer to Kurt Gödel despite the fact that the description does not fit him and in fact never did in this scenario? The reference stuck or was fixed due to a causal historical process, at the beginning of which was an intention (by Ma and Pa G) to use the name Kurt Gödel to refer to KG, and not some other person. It did not involve the descriptor “dude who discovered incompleteness,” (obviously) but at some time or another, this description was mistakenly attributed to him, and that’s how he got his rep. It’s also how most of us learn of the man’s existence. The originary intention, and the common use by non-family members of the description in association with the name, was passed down, till both reached all of us, we agreeing to go along with the practice of calling KG by the name ‘Kurt Gödel’, even if not explicitly agreeing to do so, and also assuming that the description fit him accurately.
So, once again, as in the case of the word ‘water’ but more strongly so, it is apparently true that what gives the name its established reference, has nothing to do with what is going on in our heads today, but with causal factors, historical factors, that went into determining the referent of that name, all of which trace back to the actual person KG. So, it would appear that he becomes a part of any proposition we entertain that has something to do with him. To paraphrase and amend Putnam, ‘either names just aint in the head, or persons are in my head.’ Does that sound loopy?
How might someone attempt to avoid these apparently absurd conclusions?
With regard to natural kind terms: If meanings are just in the head, then, it seems likely that they would be so, and would be individuated in virtue of descriptions that function to uniquely point out the referents, but in ways that do not have to involve the referents somehow forming part of the thought (obviously, or things would not be all that internal would they?) So, if we can come up with a description that can do the job of thoroughly individuating a proposition or thought, then we can say we have an alternative to Putnam’s partially external propositions. They would do the job his partially external propositions would do, and do it in a way that doesn’t make propositions sound like bizarre only-partially-mental things.
Way back in Grad School at Good ole’ Wayne State University, Michael McKinsey suggested this is rather easy to do. A description that would work for H2O: “The stuff to which I and other folks here on planet Earth refer with the word “water”, and which we drink and cook with, and etc..”
The pronouns "I" and "we", the phrase “folks here on planet Earth” and indeed the name “Earth” refer severally to THIS person (I point furiously at myself), THESE folks (I point at other humans around me on this planet, as they wonder about my sanity) and THIS planet (I point furiously at the ground upon which I stand, or otherwise indicate the planet) and in so doing fix or determine the reference of the word “water” by making use of these facts around me, and more specifically, the H2O around me without having to invite it into the proposition. Something similar can be constructed for the case of proper names. They end up referring to the people they refer to because we have these descriptions with demonstratives in mind. You can call these things ‘demonstrative descriptions’.
By “demonstrative” I mean that they contain words that point at things in your immediate environment that help others determine what you intend to refer to. (Actually, “I” is called an ‘indexical’ sometimes, but that is a detail that need not detain.
Ok, I’m done with Twin Earth and Philosophy of Language. Bring on the Duck Soup!