Full Idea
Human pain might be one thing. Martian pain might be something else.
Clarification
'Martian pain' would be a quite different feeling, playing the same functional role as our 'pain'
Gist of Idea
Human pain might be one thing; Martian pain might be something else
Source
David Lewis (Lewis: reduction of mind (on himself) [1994], p.420)
Book Reference
'A Companion to the Philosophy of Mind', ed/tr. Guttenplan,Samuel [Blackwell 1995], p.420
A Reaction
A key suggestion in support of type-type physicalism, and against the multiple realisability objection to the identity theory