if the term ("water") that refers to that kind of thing is a natural kind term.
We have seen that Casullo proposes to treat "experience" as a natural kind term, and Hilary Kornblith and Philip Kitcher propose to treat epistemic terms such as "knowledge" and "justification" in that way.
Of course, "acid" is a natural kind term, and we cannot have a priori knowledge of the essential nature of that to which a natural kind term refers.
Many discussions focus on the predicate kind terms, often considering them alongside other general terms, taking the principal issue to be the relationship between a natural kind term and its extension.
With a natural kind term like "water", the properties commonly associated with it (clear, odorless, colorless, thirst-quenching, etc).
The moral is: the reference of a natural kind term cannot be determined solely by what's 'in the head'.
"Experience" cannot be a natural kind term whose essence must be discoverable empirically if we are taking it in a sense relevant to epistemic justification.
He recommends that we take "experience" to be a natural kind term like "water", "aluminum", and "horse", and discover empirically what its essence is (Casullo 2003: 159).
According to Putnam, the extension of a natural kind term is fixed by ostending or otherwise identifying a sample of the kind and appealing, explicitly or implicitly, to a 'same kind relation'.
(Note that Putnam says 'same liquid relation', but that would not provide the extension of a natural kind term, since it would exclude the gaseous and solid phases of water).
