In this post, I argued that, contra Kripke, when the baptismal origin of a natural kind term has none of the properties we associate with that term, the term no longer refers to a kind that includes its baptismal origin. I then promised that I argue that, when objects not “of the same kind” (in a realist sense) as the baptismal origin of a natural kind term have all of the properties associated with a kind term, the kind term does (or at least, Kripke didn’t show that it doesn’t) include those objects in its extension. Here’s where I’ll do that.
Kripke’s Original Argument
Kripke’s example is as follows: Consider English as it was spoken pre-Lavoisier. The term “water,” at that point, clearly did not have associated with it the property of having the chemical formula H2O. The set of properties associated with it, at most, involved those properties accessible to people at the time. Now, suppose there was another compound (which Kripke calls XYZ), such that it had all of the properties of water that were accessible to people before the start of modern chemistry.
Kripke takes it as obvious (and I’m pretty much inclined to agree) that XYZ shouldn’t count as water. But should it count as water as the term was used before the start of modern chemistry? Kripke thinks that’s pretty obvious, too. Of course, he claims, the meaning of “water” hasn’t actually changed since the 17th century. So XYZ couldn’t have counted as “water” then, either, even though it had all the properties that were associated with the term.