My concern, which I interpret as being TAG’s point (but with different words), is that your example of water vs. XYZ is immediately traceable (at least for anyone who knows the philosophical discussion) to Putnam’s Twin Earth experiment. The way you express your point suggests you disregard this thought experiment—which is surprising for someone acquainted with it, because Putnam (at least when he wrote the paper) would likely agree that a substance with the same basic chemical properties of water would be water. He actually aims to provide an argument for semantic externalism—i.e., the idea that the meaning of “water” (or of other natural species) is H20, its chemical nature, and not the apparent properties commonly used as criteria to discriminate it (that it’s a tasteless liquid...). He’s so pushing against a conventionalist view about semantics (and philosophy of language), thus it’s not about physics or ontology.
My concern, which I interpret as being TAG’s point (but with different words), is that your example of water vs. XYZ is immediately traceable (at least for anyone who knows the philosophical discussion) to Putnam’s Twin Earth experiment. The way you express your point suggests you disregard this thought experiment—which is surprising for someone acquainted with it, because Putnam (at least when he wrote the paper) would likely agree that a substance with the same basic chemical properties of water would be water. He actually aims to provide an argument for semantic externalism—i.e., the idea that the meaning of “water” (or of other natural species) is H20, its chemical nature, and not the apparent properties commonly used as criteria to discriminate it (that it’s a tasteless liquid...). He’s so pushing against a conventionalist view about semantics (and philosophy of language), thus it’s not about physics or ontology.