Twin Earth

Chapter 3 is about reference. The first section contains the details of my positive view, which is a version of verificationist semantics. The following two sections reply to possible objections. They will also treat some very familiar issues like Quine s thesis about the indeterminacy of reference, the Twin Earth argument and the recent discussions about mental content... 

In the first section I shall add more details to the internal realist account. In the following one I shall deal with two objections, one posed by Quine s indeterminacy thesis and one stemming from the fact that we sometimes misclassify things. In the final section I discuss the Twin Earth argument and the causal and teleological accounts of reference. 

Nevertheless, it might seem that the present account is refuted by Putnam s famous Twin Earth argument ( The Meaning of Meaning , Philosophers ). According to the argument the following two claims cannot be simultaneously true ... 

The point may be put more sharply as follows. If we take sense to be whatever fixes reference simpliciter, than the users of Pre did not know the sense of water . What fixes the reference of a word is the justification condition in the adequate scheme. The adequate scheme is Post. They did not have Post, so they did not know the sense of water . Thus even if (1) is granted, the Twin Earth argument still does not work against my account, because (1) cannot be applied to our pre-Daltonian ancestors. 

Many have argued that mental properties can be context-dependent properties as well. Differences in one s external environment can result in the possibility of two type-identical brain states realizing two different mental states. Arguments for this view have often relied on twin-earth examples, where my doppelganger on twin earth is in a type-identical brain state as myself, yet these brain states realize different mental states. The differences in mental states are a result of slight differences in our external environments. 

Twin earth examples draw out the intuition that mental properties can be context-dependent properties. They show that it is possible for my doppelganger and me to have identical local lower level properties in our bodies and brains, but different higher-level mental properties due to differences in context Thus, mental properties do not just locally supervene on one s internal physical state, but rather globally supervene also on facts external to the person. If this is right, and mental properties can be context-dependent properties, then they too, along with many scientific properties, will resist functional reduction. 

The extensive literature in the wake of influential publications of Kripke and Putnam on natural kinds, rigid designators and Twin Earth can perhaps be seen as a continuation of the remarks of Aristotle and Locke on (predecessors of chemical) substances. Locke already used the same examples of water and gold that were the prominent examples of Kripke and Putnam. ... 

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