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. Scientific descriptions change as we find out more about the world. We may some day really discover that there are actually two different types of H2O. When we do, our first act will be coming up with names for the two types. Perhaps one of them will be called “fool’s water.”

Will that mean that the world somehow changed? Of course not. Would it mean we were wrong in calling fool’s water “water” all this time? Yes, but only because our naming practice has changed.

The world is just as it is. Delineation between distinct objects is a linguistic practice. When we discover more about the world, we express that knowledge by changing those delineations. We change the delineations by altering linguistic practice.

Putnam’s thought experiment thus tells us something interesting about how we name. It points out the relationship between how we name and what we know about the world. Our system of names is an expression of the different kinds of things we’ve found it useful to distinguish. We find it useful to distinguish between kinds when we discover facts about the world that suggest ontological subdivisions.

While interesting, none of this suggests that meaning is outside the mind.

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