Twin Earth, Part 2: The Practice of Naming

Yesterday I explained how Putnam’s Twin Earth thought experiment suggests that meaning cannot be only in the mind. I now propose an objection.

Imagine that an interdimensional alien transports water from Earth to Twin Earth, and leaves some at Agatha’s doorstep. Agatha at first calls it “water” and doesn’t have any idea that it’s anything different from the water she’s used to. However, since her body is composed largely of XYZ, not H2O, she feels sick as soon as she drinks some. She concludes this must be some different kind of water. She brings it to the community, who come up with a name for this mysteriously different water. They call it “fool’s water.”

Notice that there was only an impetus to change the name after something different was discovered about the water. Let’s change the scenario and say that H2O reacts to the Twin Earth body in the same way that XYZ does. In this case, Twin Earth doesn’t discover “fool’s water” until after certain advancements in chemistry.

The point is that Twin Earth only finds a reason to distinguish between water and Twin Earth water when they discover something that alerts them to their being two kinds.

This can always happen. For any kind of thing, we can always discover something about it that compels us to split it off into more than one type. We do that splitting by renaming.

Putnam’s error, therefore, is assuming that what the referent of a name really is is its current scientific description.…

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Twin Earth, Part 1

Hilary Putnam

There’s a debate in the philosophy of language about the meaning of “meaning.”

Specifically, it is about whether meaning is “intensional” or “extensional.” Intensional meaning is meaning as we normally understand it. If I say “beaver,” the meaning of that word is some kind of concept or sense, perhaps based on meeting certain criteria. It’s some idea in my mind. Extensional meaning is meaning based solely on reference. Thinking extensionally, the meaning of “beaver” is the collection of all things that are beavers.

The debate gets complicated and technical. Traditionally, meaning has been thought to be intensional (“internalism”). Influential arguments by Saul Kripke and Hilary Putnam, among others, have tilted the balance, such that contemporary philosophers of language tend to lean more toward “externalism”: an extensional view of meaning. In this post, I’ll quickly summarize Putnam’s argument. In a subsequent post, I’ll spell out possible objections to it.

Imagine a Twin Earth on a galaxy far, far away. Twin Earth is exactly like Earth. Everything that has ever happened on Earth has also happened on Twin Earth, down to the last detail. There is only one exception: on Twin Earth, water isn’t made of H2O. It’s made of a totally different compound, called XYZ. XYZ looks, smells, and tastes exactly like H2O. Although the chemical makeups of XYZ and H2O are distinct, there is no difference that is discernible without sophisticated equipment.

The year, on both Earth and Twin Earth, is 1750.…

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