more on this theme | more from this thinker | more from this text
Full Idea
According to externalists, Davidson's 'swampman' is your exact duplicate in brains states, but hasn't had time to become acquainted with much, so he has virtually no beliefs.
Clarification
'Swampman' is the concept of a complete human being formed by pure chance in a swamp
Gist of Idea
A spontaneous duplicate of you would have your brain states but no experience, so externalism would deny him any beliefs
Source
David Lewis (Lewis: reduction of mind (on himself) [1994], p.425)
Book Ref
'A Companion to the Philosophy of Mind', ed/tr. Guttenplan,Samuel [Blackwell 1995], p.425
A Reaction
An implausible fantasy, but it does highlight the fact that beliefs and concepts are primarily internal states.