Full Idea
Putnam claims that the Twins have different thoughts even though their heads are the same, so their thoughts (about 'water' or 'XYZ') cannot be in their heads.
Clarification
The Twins live in identical worlds, except for the chemistry of so-called 'water'
Gist of Idea
If Twins talking about 'water' and 'XYZ' have different thoughts but identical heads, then thoughts aren't in the head
Source
report of Hilary Putnam (The Meaning of 'Meaning' [1975]) by Tim Crane - Elements of Mind 4.37
Book Reference
Crane,Tim: 'Elements of Mind' [OUP 2001], p.122
A Reaction
Is Putnam guilty of a simple confusion of de re and de dicto reference?