Thursday, September 08, 2005

Alchemy World: Why Water=H2O isn't metaphysically necessary

In this post I'm going to attack the view that water and H2O are identical in all metaphysically possible worlds. I was discussing this example with some of our new first-year students last week, and they seemed fairly impressed with this case, so I'll throw it out to whatever philosophical readers I have left.

Imagine Alchemy World. It isn't another planet in our universe, like Hilary Putnam's Twin Earth, but rather a planet in a different possible universe where instead of our 100+ elements on our periodic table, there are only 4. Call them E, F, A, and W. W makes up most of the rivers, lakes, and oceans, and it falls in rain. The people on Alchemy World drink W regularly. Their lives and the macrophysical phenomena surrounding them are identical to the lives and macrophysical phenomena of people on our world until, say, 1600 AD. Of course, things are different at the microphysical level, since our world has molecules of H2O where theirs has the indivisible element W. Suppose further that the elements of their world are so constituted that if H2O suddenly appeared in their world, it would annihilate everything.

Now the question is: In their world, is water H2O or W (or both or neither)? My intuition is that W, not H2O, constitutes water in such a world. Water, I'd say, is multiply realizable across the space of metaphysical possibility. It's probably only singly realizable across the space of physical possibility, however. Alchemy World contravenes physical laws, and I don't imagine you could get another reduction base for water without contravening physical laws.

Personally, it'd be a lot more convenient for me if I accepted the metaphysical necessity of the water-H2O identity. I think aggregate hedonic improvements constitute the good in all possible worlds, and I often have to refer back to the identity of H2O to water when I'm trying to make some point about how metaphysical necessity connects to issues in epistemology and science.


Richard Y Chappell said...

I think the standard account here would say (and I would agree) that when the inhabitants use the word "water", this refers to their watery stuff W, but W is not really water (i.e. what we call "water").

Then again, I'm vaguely sympathetic towards your position too.

Neil Sinhababu said...

Yeah, that's certainly the standard view.

Richard Y Chappell said...

Granted, W certainly plays the water role on Alchemy world. But it's a different substance isn't it? I'm not sure how much sense it makes to say that a substance can be multiply realizable. Is that really what you're wanting to suggest? Or do you think of water as a role rather than a substance?

Neil Sinhababu said...

I guess the way I'd put it, Richard, is that water seems more a functional term to me than a natural-kind term. (I guess I'm unused to the locution that some entity is a role. But if songs, pies, and desires are roles, that is what I mean.)

One thing I'd add to the list, Justin, is that the XYZ example is counter-actual where my W example is set in another possible world. There might be some intuitive pull to the idea that only one fundamental elemental/molecular constitution in any world can count as water. If all the watery stuff on Earth is H2O, then only H2O can be water in our possible world. Other thisworldly watery stuffs aren't really water. But when you go into another possible world and something else makes a credible bid for status as water, while H2O itself acts really weird, the other thing can become that world's lone kind of water.

Richard Y Chappell said...

Yeah, that's a more grammatical way of putting it :)

But if water is (something like) a functional term, then couldn't it be multiply realized within a single world? If we discovered the watery-stuff XYZ or W here on Earth, wouldn't you be committed to calling them "water" too?

Anonymous said...

As a folklorist, I'm highly amused by the phrase "naive folk theory". I'm also intrigued by the problem. Not being a philosopher, I may not strictly understand the difficulty, though, so here's my naive folklorist theory...

It sounds to me like Richard is right -- you have a problem of terminology, and that problem does leave you basically having to agree that water is, or could be, multiply realized within a single world. However, if it is the case that your problem is one of terminology, then I think the solution lies in determining what connection you'd like to obtain between the term "water" and its referent(s). At the end of your post, you note:

I often have to refer back to the identity of H2O to water when I'm trying to make some point about how metaphysical necessity connects to issues in epistemology and science.

Probably this would be clearer to me if I were a philosopher, but as a naive folklorist, I react to this paragraph by being curious how exactly it is that you need to refer back to this identity in these cases. For example, if you need to say, "H2O equals water in all possible worlds, and therefore all possible environmentalists need to focus their efforts on preserving H2O," then it sounds like you should come up with a definition of water that isn't tied to the external properties of water (liquid, clear, tasty, etc.) but rather to the internal properties of water as it relates to life (provides energy during certain chemical processes, etc.). However, if you want to say, "H2O equals water in all possible worlds, and therefore all possible folklorists should investigate H2O in their researches on water mythologies," then the opposite seems to be true, since folklorists usually care about very different properties of water.

Apologies if all this was obvious already.

Anonymous said...

Addendum: My local philosopher tells me that what I've come up with is basically a (badly phrased) version of Lewis' view of this problem. Sorry to be redundant. - L.B.S.

Neil Sinhababu said...

Richard, what I said to you leaves room for water to be multiply realized within a single world. But I said to Justin that I think there's some intuitive barrier to this. A descriptivist view about proper names would probably have to incorporate some kind of uniqueness condition, so that in a world with two Caesar-like things, only the one that is the most Caesar-like counts as Caesar. I'd like to build such a condition into the semantics of "water".

Justin, isn't the original Putnam case one that involves what we'd regard as a counteractual? I seem to remember that the discovery of Twin Earth is presented as a possible future event, rather than as an alternative possibility. Since Twin Earth probably isn't actual, this is a counteractual case. (Though if Twin Earth really is out there orbiting Aldebaran or something, it's not.) I was thinking here that indicative conditionals address counteractuals while subjunctive ones address counterfactuals.

I think our intuitions are in fact triggered by different things. Replacing W with XYZ in my example doesn't change my intuitions in any significant way.

Kaitlin, I occasionally think of my dissertation as a contribution to folk psychology. (Folk science is commonsense belief on some issue that falls within the domain of science, and it's to be contrasted with real science that comes from real scientists who do real experiments.)

Is Ed Su by any chance the local philosopher over there? Good kid.

Anonymous said...

My local philosopher is my dad (who says hi), but Ed is indeed a good kid.

Neil Sinhababu said...

Whoa! I didn't realize this before, and it's too cool to go without mention. Justin and Richard, the folklorist in our midst happens to be the daughter of a highly regarded metaphysician.

Neil Sinhababu said...

I mean, I knew he was Kaitlin's dad, but I didn't associate it with the fact that we were talking about issues of metaphysical possibility.