Full Idea
The roots of externalist accounts of mental content lie in Wittgenstein.
Gist of Idea
Externalist accounts of mental content begin in Wittgenstein
Source
report of Ludwig Wittgenstein (Philosophical Investigations [1952]) by John Heil - From an Ontological Point of View 18.2 n1
Book Reference
Heil,John: 'From an Ontological Point of View' [OUP 2005], p.209
A Reaction
This points to the key idea being that content involves the whole language community, rather than that it involves the physical stuffs of the world, such as water. I suspect that Wittgenstein is right, but Putnam is wrong.