Full Idea
There seems to be nothing in the theory of direct reference to block the anti-essentialist assertion that the substance water might have been the very same entity and yet have had a different chemical structure.
Gist of Idea
Nothing in the direct theory of reference blocks anti-essentialism; water structure might have been different
Source
Nathan Salmon (Reference and Essence (1st edn) [1981], 6.23.1)
Book Reference
Salmon,Nathan: 'Reference and Essence (2nd ed)' [Prometheus 2005], p.186
A Reaction
Indeed, water could be continuously changing its inner structure, while retaining the surface appearance that gets baptised as 'water'. We make the reasonable empirical assumption, though, that structure-change implies surface-change.