Boghossian on knowing the width of water

Twin Earth, Dry Earth, and Knowing the Width of Water

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Abstract: Paul Boghossian has most explicitly and in the most careful detail argued that one can know a priori that a concept like water is wide in the sense that possessing that concept in particular requires being appropriately related to a specific type of external environment. I will show exactly where Boghossian’s argument fails and exactly where empirical presuppositions must intrude into a Twin Earth thought experiment. One cannot know a priori that a concept like water is wide by thinking about Twin Earth from the comfy confines of the philosopher’s armchair.

The content externalist claims that certain of our concepts are wide in the sense that possessing those concepts in particular requires being appropriately related to a specific type of physical or social environment. Several authors have urged that we can know a priori that a concept is wide, but Paul Boghossian has done so in the most explicit detail.[1] Boghossian argues that we can know a priori that a concept like water is wide by knowing that we can run a successful Twin Earth (TE) thought experiment on the term that expresses it. His strategy is to explicitly lay out the conditions that a term like ‘water’ must meet to be TE-eligible and argue that we can know a priori that those conditions are met. I will argue that one of those conditions, the apriority of which Boghossian takes entirely for granted, cannot be known a priori; and then I will show how the problem with that condition can be generalized to show “where exactly…empirical elements intrude into the TE experiment.” (Boghossian 1997: 277) Along the way, I will explain why Boghossian is mistaken about what an externalist can say about his Dry Earth scenario.

1. Boghossian on Twin Earth

Content externalism (CE) is most often motivated by Twin Earth thought experiments.[2] These thought experiments seem as though they can be run entirely from the armchair and yield a priori results.[3] Boghossian believes that one can know a priori that a concept is wide by knowing that the TE-eligibility conditions for the corresponding term are met. At first, Boghossian claims that there are four term-specific presuppositions involved in a successful Twin Earth experiment.[4] About the specific term ‘water’, Boghossian writes,

First, and least controversially, water and twater have to be thought of as distinct substances, distinct natural kinds; otherwise, it won’t be true that Oscar’s word ‘water’ and Toscar’s word ‘water’ have distinct extensions and referents. Second, the word ‘water’—whether on Earth or Twin Earth—must be thought of as aiming to express a natural kind concept; otherwise, the fact that water and twater are distinct natural kinds will not be semantically relevant. Third, Oscar and Toscar have to be thought of as chemically indifferent, as having no views about the chemical composition of the liquid kinds around them; other wise, they won’t end up as functional duplicates of each other in the way that the experiment requires. Fourth, the concepts expressed by the Earthly and Twin Earthly tokens of ‘water’ have to be thought of as atomic concepts, not compound concepts that are compositionally built up out of other concepts in well-defined ways. For example, the experiment presupposes that water can’t be thought of as capable of being defined as a tasteless, odorless, liquid that flows in the rivers and faucets. (Boghossian 1997: 274-275)

But later, when he goes to argue that one can know a priori that the conditions for TE-eligibility are satisfied, Boghossian draws our attention back to only three of the conditions:

What conditions does a word have to meet if it is to be Twin Earth-eligible? As we have seen, it has to be a word that expresses an atomic concept. It also has to aim to name a natural kind. Furthermore, the user of the word must be indifferent about the essence of the kind that his word aims to name; he must be chemically indifferent. (277)

He argues that one can know a priori that a specific term like ‘water’, (a) expresses an atomic concept, (b) aims to name a natural kind, and (c) can be used by one who is indifferent about the essence of the kind it aims to name. There are significant worries about the apriority of at least the atomicity condition and the aiming to name a natural kind condition (see Brown 1999). But the main worry for me, and the one which can be generalized, has to do with the condition that was overlooked when it came time to argue for apriority.

2. Knowing that Water is not Twater

Boghossian admits that ‘water’ is TE-eligible only if water and twater can be thought of as distinct, but he never argues for the apriority of this condition. I will argue in this section that one cannot know a priori that water and twater are distinct.

Water is the stuff, whatever it turns out to be, to which my uses of ‘water’ refer.[5] A successful TE thought experiment requires that there be some possible stuff to which my Twin Earth doppelganger’s uses of ‘water’ would refer. This possible stuff needs to have two features. First, it must be distinct from water; this so we can ultimately claim that my doppelganger and I express different concepts with our uses of ‘water’. Second, it must be indistinguishable from water with respect to a certain range R of superficial properties; this so we can maintain that my doppelganger and I are intrinsically identical. So a successful TE thought experiment can be run on my term ‘water’ only if there can be some stuff that is both distinct and superficially indistinguishable from water. I contend that we cannot know a priori that there is some possible stuff that is distinct but superficially indistinguishable from whatever it is to which I actually succeed in referring with my uses of ‘water’.

We can simply stipulate that some possible stuff is distinct from water, whatever water turns out to be like. Perhaps this is why Boghossian thinks that this condition of TE-eligibility is the ‘least controversial’. But we cannot go on to stipulate as well that the same stuff is R-indistinguishable from water. That would require knowing that water is not individuated solely with respect to R-properties. We would have to know, for example, that water is not just any old tasteless, odorless liquid that flows in rivers and faucets. If it were, then there could not be some substance that was indistinguishable from water with respect to these properties and still really distinct from water—anything that was a tasteless, odorless, liquid that flows in the rivers and faucets would have to be water. Since I cannot know anything about the underlying nature of the stuff to which I actually refer with my uses of ‘water’ without empirical investigation of my external environment, I cannot know a priori that water is not individuated solely with respect to R-properties. So I cannot know a priori that there can be some stuff that is R-indistinguishable but really distinct from water.

At this point Boghossian will try to fall back on the atomicity condition of TE-eligibility and argue that we can in fact know a priori that water is not just any old tasteless, odorless liquid that flows in the rivers and faucets because we can know a priori that ‘water’ expresses an atomic concept. The concept expressed by ‘water’, according to the atomicity condition, cannot be “defined as a tasteless, odorless, liquid that flows in the rivers and faucets.” Since we can know that the concept expressed by ‘water’ is atomic, we can know a priori that water is not just any old tasteless, odorless liquid that flows in the rivers and faucets.

The problem with this objection is that it subtly confuses syntax and semantics. To maintain the apriority of concept compositionality, Boghossian must have in mind a syntactic notion. So when he says that ‘water’ cannot be defined as a tasteless, odorless liquid that flows in the rivers and faucets, he must mean that the concept expressed by ‘water’ is not simply the syntactic composite of the concepts expressed by “tasteless, odorless, liquid that flows in the rivers and faucets.” It is perfectly possible however, as I will show later, for a term to express a syntactically atomic concept that is nevertheless semantically equivalent to some syntactically composite concept. It is perfectly possible for the term ‘water’ to express a syntactically simple concept and yet refer in all possible worlds to all and only tasteless, odorless, liquids that flow in rivers and faucets. Simply knowing that ‘water’ expresses an atomic concept does not tell us anything about the semantic extension of the term or the individuation of the stuff to which the term refers.

3. Boghossian on Dry Earth

I have just argued that one cannot know a priori that water and twater are distinct because one cannot know a priori that there can be some stuff that is R-indistinguishable but really distinct from water. Let me now argue for that point in a slightly different way, using Boghossian’s Dry Earth scenario, so that I can raise Boghossian’s objection in terms of his argument about what an externalist cannot say about Dry Earth.

Here is my argument: Dry Earth is a situation where there appears to be a tasteless odorless liquid flowing in the rivers and faucets, but there is really nothing there—it is a complex hallucination. Still, the people on Dry Earth use ‘water’ in all the same narrowly described ways as we do. That is, they use ‘water’ to talk about the tasteless, odorless liquid that they believe flows in their rivers and faucets. The residents of Dry Earth used some description like “the tasteless, odorless liquid that flows in the rivers and faucets” to fix the reference of their term ‘water’; but there was nothing in their environment for that description to pick out. If we imagine, as the story is told, that Dry Earthlings nevertheless continue to use the expression ‘water’ in all the same narrowly described ways as we do, then we must admit that their uses of ‘water’ are in fact meaningful and do express some concept. I contend that the term ‘water’ as it is used on Dry Earth must express a concept that refers in any possible world to all and only tasteless, odorless liquids that flow in rivers and faucets.[6] The description that was intended merely as a reference-fixing device has in fact, and perhaps unbeknownst to the Dry Earthlings, become the de facto definition or semantic analysis of the term. The stuff to which Dry Earthlings actually succeed in referring with their uses of ‘water’ is individuated solely with respect to a certain range R of superficial properties. There cannot be a stuff that is R-indistinguishable but really distinct from the stuff to which Dry Earthlings actually succeed in referring with their uses of ‘water’.

Now if we happen to be in, and to have always been in, a Dry Earth scenario, then our term ‘water’ actually refers to a stuff that is individuated solely with respect to a certain range of superficial properties. So if the actual world, contrary to what believe, turns out to be like Dry Earth, then there cannot be a substance that is superficially indistinguishable but substantially distinct from water. Since I cannot know a priori whether the actual world is like Dry Earth, I cannot know a priori whether there can be stuff that is superficially indistinguishable but substantially distinct from water.

Boghossian would certainly object to my contention that the Dry Earthlings uses of ‘water’ turn out to refer to all and only tasteless, odorless liquids that flow in rivers and faucets. He himself believes that this is the right thing to say about the Dry Earth scenario, but he argues that the content externalist cannot say it:

“...the Twin Earth externalist is committed...to holding that ‘water’ expresses an atomic concept under conditions where it has a non-empty extension...That is one of the presuppositions of the Twin Earth thought experiment. But, then, how can the very same word, with the very same functional role, express an atomic concept under one set of external conditions and a compound, decompositional concept under another set of external conditions? A concept’s compositionality is exclusively a function of its internal ‘syntax’, and can’t be contingent upon external circumstances in the way that the present proposal would require.” (Boghossian 1997: 281)

Boghossian’s argument here can be fairly laid out as follows:

P1: If ‘water’ has the same functional role in two different external circumstances, then it cannot express an atomic concept in one but a compound concept in the other.

P2: The externalist is committed to saying that ‘water’ expresses an atomic concept on Earth.

C1: So the externalist must say that ‘water’ also expresses an atomic concept on Dry Earth.

P1 is supposed to follow from the idea that a concept’s compositionality is solely a function of its internal ‘syntax’. There is an assumption at work here that the functional role of the term that expresses a concept determines the internal ‘syntax’ of the concept (whatever exactly that is supposed to be). Boghossian is assuming that if two terms have the same functional role, then the concepts they express have the same internal syntax. That is what is needed to move from same functional role to same compositionality, as in P1. It is not at all obvious to me that the assumption here is so unproblematic that it can go without argument, as it does. It can seem relatively unproblematic to hold that internal syntax (of concepts, understood as elements of a language of thought) determines functional role, but Boghossian is implicitly relying on the converse of that. And that seems much more problematic, especially in the present context. For, an externalist may well want to say that ‘syntactic’ features of concepts are determined in part by the social/physical environment to which one is appropriately related.

There are problems, I think, with justifying P1; but I am willing to concede it. Let’s say that C1 above is true. We do not yet have an objection to my claim that ‘water’ on Dry Earth refers in any possible world to all and only tasteless, odorless liquids that flow in rivers and faucets. What is needed to complete Boghossian’s objection is the following:

P3: If on Dry Earth ‘water’ refers to all and only tasteless, odorless liquids that flow in rivers and faucets, then ‘water’ expresses a compound concept on Dry Earth.

Boghossian could then combine this with C1 above to yield:

C2: So an externalist cannot say that on Dry Earth ‘water’ refers to all and only tasteless, odorless liquids that flow in rivers and faucets.

Here again, however, is Boghossian’s subtle confusion of syntax and semantics. Just because a certain term is semantically co-extensional with a complex description does not mean that the concept expressed by the term is a mere syntactic composite of the concepts expressed by the constituents of the description. It is possible to imagine, for example, that someone expresses an atomic concept with her uses of the term ‘bachelor’ even though that term is co-extensional with the description ‘unmarried (adult, human) male.’ It is conceivable that someone could acquire the concept bachelor first, and then acquire the concepts male and unmarried in part through her grasp of the concept bachelor, with the help of her grasp of concepts like spinster and husband . One could learn the concept unmarried as applying to anything that is either a bachelor or a spinster; and one could learn the concept (adult, human) male as applying to anything that is either a bachelor or a husband. Thus we can imagine that bachelor is an atomic concept for someone, and not merely a compound of the concepts unmarried and male, even though it refers to all and only unmarried males. A term can be semantically co-extensional with a description without expressing a concept that is the syntactic composite of the concepts expressed by the description.

The upshot then is this: An externalist can say both that ‘water’ on Dry Earth expresses a syntactically atomic concept and that the semantic extension of that concept is all and only tasteless, odorless, potable liquids. So Boghossian is mistaken when he claims that an externalist cannot say that ‘water’ on Dry Earth refers to all and only tasteless, odorless liquids that flow in rivers and faucets. My argument remains intact—if the actual world turns out to be like Dry Earth, then our uses of ‘water’ refer to a stuff that is individuated solely with respect to a certain range of superficial properties; and since I cannot know a priori whether the actual world is like Dry Earth, I cannot know a priori whether there can be some stuff that is superficially indistinguishable but substantially distinct from the stuff to which we actually succeed in referring with our uses of ‘water’.

4. Conclusion

I have up to now been arguing specifically that one cannot know that water is wide on the basis of a TE thought experiment, because one cannot know a priori that twater is not water.[7] The problem with knowing a priori that twater is not water generalizes: One cannot know a priori that any concept is wide on the basis of a TE thought experiment, because one cannot know a priori whether there can be some stuff that is distinct but superficially indistinguishable from the stuff to which some term actually succeeds in referring.

Imagine that a subject S uses a term T to express a concept C and that S explicitly associates a range R of properties with c-stuff (i.e., the stuff to which C refers). To show that C is wide, a successful TE thought experiment must describe a possible subject S* who meets two conditions. First, S* must be intrinsically identical to S and use T in all the same narrowly described ways as S. Second, S*’s uses of T must have a different extension from S’s uses of T. These two conditions can be jointly satisfied only if there can be some stuff that is distinct but R-indistinguishable from c-stuff. That is, one can know a priori that C is wide only if one can know a priori that c-stuff is not individuated solely with respect to its R-properties.

But one cannot know a priori that some stuff is not individuated solely with respect to a specified range R of properties. Even if one explicitly intends a term to express a concept that refers to some stuff that is individuated more precisely or more finely than R-stuff, it can still turn out that one expresses a concept that refers to all and only R-stuff, as is the case in the Dry Earth scenario. On an externalist account, concepts are individuated in part by specific features of one’s external environment; and so the extension of a term may turn out to be quite different from what one narrowly intends or believes. To know that there really is more to being c-stuff than merely having R-properties requires knowing something about the stuff to which T actually refers. Given that T expresses a wide concept, what T actually succeeds in referring to depends on some relatively specific features of our actual environment. Since one cannot know a priori anything very specific about one’s external environment, one cannot know a priori that there is more to being c-stuff than merely having R-properties. One cannot know a priori that c-stuff is not individuated solely with respect to R-properties; and so one cannot know a priori that C is wide on the basis of a TE thought experiment.

Twin Earth thought experiments require that there be some possible stuff that is superficially indistinguishable but nevertheless distinct from that to which one actually succeeds in referring with her uses of a certain term. This is where empirical elements intrude into the TE thought experiment. For this requires knowing something about the nature of the stuff to which one actually succeeds in referring with a certain term, and that requires some empirical investigation of one’s actual environment. So it is that we cannot know that a concept like water is wide simply by thinking about Twin Earth from the comfy confines of the philosopher’s armchair.

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