Swampman is the subject of a philosophical thought experiment introduced by Donald Davidson in his 1987 paper "Knowing One's Own Mind". In the experiment, Davidson is struck by lightning in a swamp and disintegrated; simultaneously, an exact copy of Davidson, the Swampman, is made from a nearby tree and proceeds through life exactly as Davidson would have, indistinguishable from Davidson. The experiment is used by Davidson to claim that thought and meaning cannot exist in a vacuum; they are dependent on their interconnections to the world. Therefore, despite being physically identical to himself, Davidson states that the Swampman does not have thoughts nor meaningful language, as it has no causal history to base them on.
The experiment runs as follows:
Suppose lightning strikes a dead tree in a swamp; I [Davidson] am standing nearby. My body is reduced to its elements, while entirely by coincidence (and out of different molecules) the tree is turned into my physical replica. My replica, The Swampman, moves exactly as I did; according to its nature it departs the swamp, encounters and seems to recognize my friends, and appears to return their greetings in English. It moves into my house and seems to write articles on radical interpretation. No one can tell the difference. But there is a difference. My replica can't recognize my friends; it can't recognize anything, since it never cognized anything in the first place. It can't know my friends' names (though of course it seems to), it can't remember my house. It can't mean what I do by the word 'house', for example, since the sound 'house' it makes was not learned in a context that would give it the right meaning--or any meaning at all. Indeed, I don't see how my replica can be said to mean anything by the sounds it makes, nor to have any thoughts.— Donald Davidson, Knowing One's Own Mind