Older, but Revived Nonetheless.

(The best resource in the last few decades for understanding modern global skepticism is probably Barry Stroud's book. This essay is in part inspired by Ebbs-style semantic antiskepticism.)
On Putnam's [one-time] view of meaning, a word's meaning is not some feature of or thing in the mind, but rather an object to which the word applies. The thing to which the word properly applies is that which is typically and causally related to thinking/uttering the word. As an example, the word 'water' applies to (portions of) water. A word is correctly applied just in case the thing it is said of is indeed what the speaker (implicitly) claims it to be. So if I say that that puddle over there is made of water, my use of 'puddle' will be correct if the thing indicated is a puddle and my use of 'water' will be correct if the puddle is composed of water. The proposition I express by saying 'that puddle is water' is true just in case the thing about which I am talking is a puddle made up of water. This is of course an example of the disquotational principle, where supposing 'x is F' has a unique meaning: 'x is F' is true (when uttered by A) iff x is F (in the realm of objects to which A can refer). The reason for this seemingly odd formulation is that the realm of what is (can be) mentioned by words will vary to some degree with language. For instance, a brain in a vat under certain circumstances will be speaking a different language from our own (English) and will refer to (at least some) things such that a string of words will mean something different from that string of words in English so that the truth-conditions of what is expressed by the utterance of the string will be different for the brain than for we English speakers.

Putnam denies the Cartesian thesis that meaning is determined by a mental image by counterexample. Briefly, if A and A's identical Twin-Earth counterpart A* utter the same word, it may be the case that even though they have identical mental images what they mean differs [I derive this version of the example from in large part, Putnam's "The Meaning of 'Meaning' " with many thanks to discussions with Gary Ebbs]. Supposing that on Twin-Earth there is a liquid, let us call it Twin-water, that in all respects (in A*'s experience) is identical to the liquid H20 (that is, water) on Earth (in A's experience) although Twin-water is chemically dissimilar, and that when A and A* utter 'water' they have the same mental image: it will be the case that they are mentioning a (portion of) something different in all cases, and the word 'water' refers to different things despite the similarity of the mental images. (I will set aside complications and take it that this is sufficient for our purposes here to show that meaning of a word is not determined by a mental image associated with its use.) Putnam's view, very roughly, is that the meaning of a word is determined by the circumstances under which it is used.

Anthony Brueckner reconstructs an argument that superficially looks like Putnam's but has certain important differences. What seems relevant to me is not that he relies on the idea of sense impressions to do a great deal of work that Putnam doesn't have them doing, regarding (dis-)confirmation of whether one is a brain in a vat [A. Brueckner, "Brains in a Vat" 151]. Rather, the telling blow can be dealt at the point at which Brueckner tries to undercut Putnam by claiming that one is not allowed to assume that we are speaking English in making the anti-skeptical argument. His claim is that application of the disquotational principle to A's statement 'I am a brain in a vat' by A will not work since A would be assuming that A spoke English even though this may not be the case [Brueckner 164]. If something seems wrong here, good: it seems appropriate to ask now how could actual-world-interacting A not assume she is speaking English, and how B could not assume he is speaking 'English' (which we can call Venglish)? Finally, Brueckner claims that, under the conditions he has described, in which what language used to show that 'I am a brain in a vat' is false is unknown, it cannot be shown that we know what we mean by our words [165-6].

Now the actual results of Putnam's argument. The problem that Putnam's argument seems to me to raise for the skeptic just is whether the skeptic about knowledge of the empirical world can even raise the always-in-a-vat case as in intelligible possibility. As he says, the point is to consider "the preconditions for thinking about, representing, referring to, etc." (Putnam 16). But we have been assuming all along the the skeptic about empirical knowledge raises an intelligible possibility, which seems immediately gripping as the skeptic who employs arguments about dreaming seems to raise an immediately gripping intelligible possibility.

The skeptic cannot raise an intelligible problematic possibility using the words 'brain in a vat'. Now, since B's words 'brain' and 'vat' cannot refer to actual brains in vats, he cannot in fact raise this skeptical possibility, because his words just can't mean that. If B formulates the argument using the words 'vat', 'english', 'Venglish' and so forth, we can see how B fails to raise a skeptical doubt. Now since B's mental images are just like A's (and A is in our actual world) is seems that B can picture what looks (to A) like a brain in a vat, and B will call it 'brain in a vat', but B's words will be about a brain in a vat in the image. Similarly B will refer to Venglish in the image by 'Venglish'. Note that whatever theory of meaning one uses, for B 'Venglish' means a language other than his own, just as what A means by 'Venglish' is a language other than English (her own language). In B's realm of reference, 'I am a brain in a vat' is false because 'brain in a vat' refers to something that is obviously not the case with him. There is (ex hypothesi) no evidence that he gets that would indicate that he is a brain in a vat, but there is also no evidence that he gets that would indicate that he is a brain in a vat in the image (what he calls 'brain in a vat'). But given that one's beliefs (that are expressable) are limited to what one is able to understand the meaning of, there is no way, in the situation under consideration, for B to believe, and worse even to understand, the proposition that he is a brain in a vat, since he cannot mean in interior expressions brain in a vat, but is limited to meaning brain in a vat in the image. What this amounts to is that whatever one can mean by 'brain in a vat', this possibility is false of oneself.

For A, speaking English, can talk about brains in the image and about actual brains, and so forth. B can talk about brains in the image in the image and about actual brains in the image, and so forth. But it doesn't matter what language the proposition that one is a brain in a vat is expressed in–whatever the content of that proposition is will not be true. It seems to me that Brueckner gets himself into trouble by making a great deal of noise (only mentioned in a footnote) about language while trying to use a "metametalanguage" to describe what's going on in his argument (ft. 20 on 162-3). But we can express the idea in plain English: whatever it is that I mean when I say 'I am a brain in a vat', I am not that, so the proposition is false. The application of the disquotational principle seems to fail because the skeptic about knowledge of one's own beliefs tries to look at the statement 'I am a brain in a vat' from a "metaliguistic" standpoint, while not realizing that, even from that standpoint the proposition that one is a brain in a vat must be false, again because whatever is meant by 'brain in a vat' is not the case of one's own "brain". What this shows, if it is right, is that the skeptic about knowledge of one's own beliefs cannot raise an intelligible alternative to the case in which I do know what my words mean.

A further step is required to see why. B is limited to understanding (and believing to be true or false) just that which B can express. This does not include the proposition that B is a brain in a vat, but does include the proposition that B is a brain in a vat in the image, which B would express by saying 'brain in a vat'. Suppose we assume that A can by analogy believe herself to possibly be in a situation akin to B's. Then what we would be saying is that she, unlike B, can understand some kind of (imagined) uberwald-vats in which her uberwald-brain resides. However, B can imagine things that appear to B just as these imaginings appear to A, and he can say 'uberwald-vats' and so forth, but he cannot mean what A in the actual world means by them. What this seems to show is not that we have superior powers of intuition and insight, but rather that we do not understand what we imagine. That is to say, if the situation is really supposed to be analogous (one, after all, proposed to be "a brain in a vat"), then what the skeptic about empirical knowledge attempts to assert as a possibility is unintelligible; and the skeptic about knowledge of one's own beliefs relies on this alternative. A skeptic in a vat could not raise the possibility that B is a brain in a vat, because that would be unintelligible to both skeptic and B. Similarly, the skeptic about knowledge of one's own beliefs cannot raise the possibility that she thinks she understands related (somehow) to "uberwald-vats" and so forth. 'I am a brain in a vat' is unintelligible or false (no just false since the string of words might fail to express something one can understand). So in order to get this skeptical argument off the ground–based on the "results" of Putnam's argument as Brueckner construes it–the skeptic now has to assert that what is shown to be unintelligible, and necessarily so, is in fact intelligible. And even assertion of a super-knower cannot make that less than utterly wrong.

[This discussion does some violence to Brueckner in the sense that his argument is not fuly exegized with quotations and cetera, but any careful reader of the work should see that my interpretation is not malicious, quite the opposite. Of course I do (I now realize) have certain systematic reasons for wanting some form of epistemic externalism to work with.]


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