Twin-Earth Thought Experiments:
Annotated Bibliography   by Bryan Frances

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There have been many dozens of articles written on the Twin-Earth thought experiments and their putative consequences. In this bibliography I limit myself to three kinds of works: those with helpful comments on the reasoning in the thought experiments, those that introduce the main issues generated by the thought experiments, and those parenthetically alluded to in the text above (which do not have detailed descriptions unless they fall into one of the first two categories). For those new to the topic, I highly recommend reading, in order, Putnam 1975, Burge 1979, Burge 1982a, and Burge 1982b. In order to introduce oneself to the main implications of the thought experiments, one should go on to read, in any order, Burge 1988 (self-knowledge), Loar 1988 (commonsense reasons for narrow content), McLaughlin and Tye 1998 (self-knowledge again), Fodor 1987 (causation and scientific reasons for narrow content), and Burge 1993 (physicalism).


Putnam, Hilary (1975), "The Meaning of 'Meaning' ", reprinted in his Mind, Language, and Reality (Cambridge: Cambridge University Press): 215-271.

This is indispensable; it is the article that started it all (although seeds of Twin-Earth thinking were present in some of Putnam's earlier works). Putnam gives his Twin-Earth thought experiments involving the water-XYZ, aluminum-molybdenum, and elm-beech pairs. Little attention has been paid to the latter thought experiment. This is unfortunate since one can use it to generate dual-concept thought experiments (see section I above), which provide the most convincing arguments. In this article Putnam's discussion is a bit rough, as it often is when he is breaking new ground. Much of what he says is not compatible with anti-supervenience or externalism; and much of what he says confuses the two. Even so, it is rightly regarded as a philosophical classic.

Burge, Tyler (1979), "Individualism and the Mental," in French, et al., eds. Midwest Studies in Philosophy: Studies in Metaphysics (Minneapolis: University of Minnesota Press): 73-122.

This article is indispensable. Burge sets out in detail his thought experiments purporting to show that by altering the linguistic rules of one's society-without altering one's intrinsic physical makeup-one could have ended up with different thoughts. Burge counters many criticisms and applies his theory to the token identity thesis, claiming that his anti-individualism refutes that form of physicalism. Many critics have targeted this article, but no criticisms have stuck. For some reason I don't know, virtually no one has responded to his argument that anti-supervenience rules out token identity physicalism.

Putnam, Hilary (1981), Reason, Truth, and History (Cambridge: Cambridge University Press).

In the first chapter of this work Putnam does two important things. First, he offers a general argument that individualistic theories of meaning are "magical" in the sense that it would be magic if the purely intrinsic properties of something could give it intentionality, aboutness, or content. Second, he offers his famous proof that in a certain sense radical scepticism is self-refuting. Roughly put, the argument is as follows. The Twin-Earth stories show that in order to think thoughts about water, one must have had some kind of contact, direct or indirect, with water or hydrogen or oxygen or something like that. Brains in a vat have never had such contact; so they cannot think about water. Thus, if we were brains in a vat, then we could not think or say that we are brains in a vat. Since we know by privileged access that we believe that water is clear, for instance, we know that we have water thoughts. So we can conclude by a simple rule of logic that we are not brains in vats. Putnam did not quite say that this reasoning is purely a priori, but it's close enough to make it look (to many philosophers) as if we are proving that we are not brains in vats using very general considerations about the metaphysics of meaning. This is surprising and thus has led to a large literature, mostly critical, of Putnam's argument.

Burge, Tyler (1982a), "Other Bodies," in Woodfield, ed. Thought and Object (New York: Oxford University Press): 97-120.

This article is indispensable. Burge explains his position on externalism, the idea that having a thought requires that your environment satisfy some empirical conditions. He also clarifies what externalism and anti-individualism are and relates them to de re belief. He evaluates Putnam's thought experiments, which are different from his own in that only the former focus on counterfactual changes in the natural kinds in one's environment. The idea that Putnam's thought experiments show that natural kind terms are somehow indexical is criticized here. This article is best read after reading Putnam's original work on externalism, "The Meaning of 'Meaning'".

Burge, Tyler (1982b), "Two Thought Experiments Reviewed," Notre Dame Journal of Formal Logic, 23, 284-293.

This article is helpful in eliminating various initially tempting but erroneous criticisms of both Putnam's natural-kind and Burge's linguistic-rule thought experiments. It is best read right after reading Burge 1979, 1982a, and Putnam 1975.

Fodor, Jerry (1982), "Cognitive Science and the Twin-Earth Problem", Notre Dame Journal of Formal Logic, 23, 98-118.

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McGinn, Colin (1982), "The Structure of Content", in Woodfield, ed. Thought and Object (New York: Oxford University Press): 207-258.

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Owens, Joseph (1983), "Functionalism and the Propositional Attitudes," Noûs, 17, 529-549.

Owens offers a detailed and convincing argument that functionalism is false if anti-individualism is true. In particular, he argues that there is no way to characterize the inputs and outputs the functionalist needs so as to avoid the refutation from anti-supervenience.

Burge, Tyler (1986a), "Individualism and Psychology," The Philosophical Review, 95, 3-45.

In this article Burge argues for several central claims, the general point of which is that psychology can get along fine being anti-individualistic. First, theoretical psychology appeals to non-supervenient content properties all the time. Second, the arguments that purport to show that psychology must, in order to be a real science, appeal to only supervenient properties are inadequate. Third, David Marr's theory of vision appeals to non-supervenient properties. Fourth, there is a general argument against visual theories respecting supervenience. This is a difficult article to read; much more so than the earlier ones.

Burge, Tyler (1986b), "Intellectual Norms and Foundations of Mind," The Journal of Philosophy, 83, 697-720.

In this article Burge has given yet another kind of thought experiment, one that does not depend on the protagonist's lack of expert knowledge of a kind (e.g., of walleye, water, aluminum) or (Burge claims) lack of expert knowledge of a meaning (e.g., of 'arthritis', 'contract') but on her having a "nonstandard" (i.e., radically incorrect) theory regarding an item referred to by her belief (e.g., concerning sofas). The person's theory is odd enough that she doubts what might be thought necessary truths about the subject (e.g, doubts that sofas are furniture). I suspect that the primary point of this third kind of thought experiment is twofold: if sound it expands the class of terms and beliefs subject to Twin-Earth thought experiments, and it shows another way that thought is dependent on one's relations to one's socio-linguistic environment.

Davidson, Donald (1987), "Knowing One's Own Mind," Proceedings and Addresses of the American Philosophical Association, 60, 441-458.

Davidson has quite a bit to say about self-knowledge and the Twin-Earth thought experiments, although virtually everyone feels that he misinterprets and underestimates Burge in this article. He also tries to show, contrary to the argument in section 4 above, that we can have token identity (mental tokens are physical as well) with anti-supervenience and the idea that mental tokens have their non-supervenient contents necessarily. I and many others regard the argument as a failure. He also has much to say against the Cartesian theater concept of mind.

Fodor, Jerry (1987), Psychosemantics (Cambridge: The MIT Press).

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Burge, Tyler (1988), "Individualism and Self-Knowledge", The Journal of Philosophy, 85, 649-663.

The problem addressed here is deceptively simple. According to Burge our thought contents depend on the physical world external to the knower: vary the world and the contents vary even if the knower's physical makeup remains the same. So doesn't that mean that in order to know our thought contents we would have to know something significant about our environment-viz. what relations we stand in to the environment? And isn't that incompatible with the directness and authority of our knowledge of our thought contents? Burge argues that the tension here is illusory; we can have both anti-individualism and directness and authority. Here we find the first extended discussion of the switching cases mentioned near the end of section 4. Here we also find Burge's interesting argument that in a restricted but important class of cases we cannot be wrong about what thought contents we are entertaining. Roughly, if one thinks that one thinks that P, then one's thought about one's thought is true (he doesn't say justified because he thinks that is a much more complex issue) because in order to even have the second-order thought one must have the first-order thought (e.g., in order to satisfy "I think that I think that water is clear", one must satisfy "I think that water is clear").

Loar, Brian (1988), "Social Content and Psychological Content," in Grimm and Merrill, eds. Contents of Thought (Tucson: University of Arizona Press): 99-109.

In this deservedly influential article Loar argues via several kinds of thought experiment inspired by the Twin-Earth ones that there are two kinds of belief content. One is anti-individualistic, just like Burge says, but the other is more relevant to ordinary psychological explanation and probably is individualistic. For instance, if the only difference between me and my Twin-Earth twin is that absolutely everything I believe about and desire of walleye, he believes about and desires of sauger, and neither of us could distinguish the fish even if our lives depended on it, then in some interesting and philosophically relevant sense our beliefs about fish pack the same explanatory punch despite being of distinct belief types. Even though I but not my duplicate believe that walleye are freshwater fish-so we differ in one kind of truth-conditional content-this difference between us is somehow explanatorily irrelevant. There must be some kind of psychologically relevant content shared by me and my Twin-Earth twin. Loar's arguments and theses have been found wanting, but their intuitive force is strong.

Burge, Tyler (1989), "Individuation and Causation in Psychology", Pacific Philosophical Quarterly, 70, 303-322.

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Wallace, John and H.E. Mason (1990), "On Some Thought Experiments about Mind and Meaning", in Anderson and Owens 1990, 175-200.

Wallace and Mason bring up some utterly novel criticisms of the thought experiments; primarily, that the counterfactual reasoning used is bizarre in various ways. This article has fallen dead-born from the press, as it may be said, even though no one has explained why. My guess is that everyone feels as though Wallace & Masons' criticisms somehow miss the point; that they do not really engage what the reasoning for anti-individualism is about. Even so, if this is true then we ought to be able to characterize the reasoning behind the thought experiments so that it is transparent why the Wallace-Mason criticisms miss their mark. No one has done this as of 1999 and it is not straightforward how to do it.

Fodor, Jerry (1991), "A Modal Argument for Narrow Content", The Journal of Philosophy, 88, 5-26.

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McKinsey, Michael (1991), "Anti-Individualism and Privileged Access", Analysis, 51, 9-16.

This is the article that started the project of analyzing the following argument. If one knows a priori the externalist thesis that if one thinks that water is clear then there is a physical world satisfying certain empirical conditions, then if one knows a priori that one thinks that water is clear, then one should be able to deduce a priori by modus ponens that there is a physical world and even that one's physical world satisfies certain empirical conditions. But since that conclusion is doubtful, one may think that the argument must be unsound. The privileged access premise and the deduction seem solid; so McKinsey suspects that the externalist thesis is not knowable a priori. He concludes that something is wrong with externalism, since the thought experiments generating the externalist theses seem a priori. McKinsey's treatment of the issue is somewhat crude, but he deserves credit for bringing to attention a problem that forced a probing analysis of externalism and its a priority.

Burge, Tyler (1993), "Mind-Body Causation and Explanatory Practice," in Heil and Mele, (eds.) Mental Causation (New York: Oxford University Press).

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Burge, Tyler (1995), "Reply: Intentional Properties and Causation," in Macdonald and Macdonald, (eds.) Philosophy of Psychology (Cambridge, MA: Basil Blackwell, Inc.).

This is Burge's reply to Fodor 1991.

Wilson, Robert (1995), Cartesian Psychology and Physical Minds (New York: Cambridge University Press).

Wilson approaches the supervenience issue from a philosophy of science perspective, trying to show that a serious scientific study of thought need not be individualistic, as Fodor said it had to be.

McLaughlin, Brian and Tye, Michael (1998), "Externalism, Twin-Earth, and Self-Knowledge", in Wright, Smith, and MacDonald (eds.) Knowing Our Own Minds, pp. 285-320. Oxford University Press, Oxford.

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Frances, Bryan (1999), "On the Explanatory Deficiencies of Linguistic Content", Philosophical Studies, 93, 45-75.

In this article I attempted to counter the arguments of Loar 1988. My main thesis is that the intuitive considerations revealed by Loar and thought to demand a kind of individualistic content alongside Burge's anti-individualistic content can be satisfied without positing any kind of content other than the anti-individualistic one.

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