Swamp man
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Swamp man is the title given to a philosophical thought experiment about causality and personal identity, first put forward in this form by Donald Davidson:
Suppose Don goes hiking in the swamp and is struck and killed by a lightning bolt. At the same time, elsewhere in the swamp another lightning bolt spontaneously rearranges a bunch of molecules such that, entirely by coincidence, they take on exactly the same form that Don's body had at the moment of his untimely death.
This "swamp-man" will walk out of the swamp, return to Don's office at Berkeley and write the same essays he would have written; will interact like an amicable person with all of Don's friends and family, and so forth. Does it in fact have a mind? When it makes English-like noises, is it saying things? Is it a person?
At first blush we would be inclined to affirm all these things. But take a fairly specific example. Suppose at some point the previous day Don had looked at a glass marble on a shelf; unbeknownst to him there was another, visually identical glass marble hidden right behind it. When Don says, "that marble I saw yesterday," he is referring to the one that he did see, even if he could not supply enough descriptive information to identify it later. This is because in judging the reference of a word we take into account the causal history of its user. It is possible that the marbles might have been in the opposite positions when Don saw them; if they had been, he would have been referring to the other one. Furthermore, it is possible that if this had happened, Don's physical state might have been utterly identical to the way it in fact turned out. This means that the physical state of a person is not sufficient to fix the meanings of their words. We must take their causal history into account.
The swamp man has no causal history of the sort that would allow us to determine what his words mean. In principle, the philosopher Donald Davidson tells us, the above indeterminacies can be extended to any degree we like: the fact that the swamp man happens to be identical to Davidson does not change the fact that he could have arrived at that state by any one of countless histories, each of which would demand we interpret him differently. Until Swamp-Don has begun interacting with and using language among the objects of the real world, we can have no grounds to attributing any mental state at all to him.
This is essentially an argument for externalism as regards meaning - the claim that what one's words mean is determined not by some internal state, but rather by the causal history of how the words were acquired by the speaker.
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An alternate explanation
If the swamp man has exactly the same form that Don's body had at the moment of his untimely death (i.e., it is a molecule for molecule copy), it has the exact same mind that Don has. When it makes English-like noises, they are no different from the English-like noises that Don would have made. It is as much a person as Don is.
When we hear someone's words (whether Don or the swamp man), certain responses are produced in us. Some of these are private and others are public. As for taking "into account the causal history of its user", what does this mean? How do we do this? How can we do this? We don't do it. If we get directions in an unknown location from a perfect stranger, we may follow the directions without knowing anything about the causal history of the stranger. We seldom know about the causal histories of the people we deal with. If we have had bad interactions in the past with people who look like the stranger, we may not follow the directions. However, this has nothing to do with the causal history of the stranger.
Recall that the basic premise (of a molecule by molecule copy of Don being made) is an impossibility. However, if this impossibility happens, that the resulting swamp man had no causal history is of absolutely no concern. Causal histories make changes in the body of the person undergoing the history (including his nervous system). In this hypothetical case, the changes get made by the lightning. The key thing to realize is that the result is the same as Don, in every way, in form and function, at the time of creation. As he starts/continues living, he will undergo a history, his body will undergo changes (the normal way this time), and his personality will start drifting from what it was at the time of the creation of the swamp man.
A further variation (which addresses the issue of the causal history) is to argue that, because the original Don's history caused his body (including his nervous system) to form into the arrangement that was struck by the lightning, and that because a condition of the scenario is that the swamp man is an exact replica (if there are any differences between it and the original Don, it no longer falls into this scenario), the swamp man DOES have a causal history -- and he shares it with the original Don. That is to say, if the original Don had experienced a different history, thus resulting in a physically different original Don, the swamp man would necessarily share those differences as well. Don's history causes the swamp man to be what it is -- again, at least as far as this scenario is concerned -- and as a result, the two are inextricably linked. Indeed, the division between the two becomes questionable; they could in fact be considered one person, who happened to be part of an event we initially perceive to involve two separate entities, when it fact those two entities are no more separate than a child is separate from his adult self (even less extremely so, as this scenario involves only an instant).
Additional Concerns
The fact that the second lightning bolt creates the "swamp-man" at any particular time has no causal relation to what happens to Don. In fact, the "swamp-man" would be exactly the same in all regards even if Don was never hit by the lightning. In this case two people, who are much alike, would walk out of the swamp. Suppose Don is hit by a car just as he steps from the swamp. Again, this event changes nothing to the "swamp-man", assuming that he never saw Don or the car accident. Don's friends will greet the "swamp-man" as Don and they all will never know what happened in the swamp.
However, the personal experience of Don was that he died in a car accident. Or that he died struck by a lightning bolt. A careful approach to the matter of personal identity should account for the personal experience of each involved individual separately. Too often only the experience of the surviving copy, the "swamp-man", and his friends is considered, ignoring the fact that the personal experience of Don himself ends in a death.
See also
External links
- Thorough analysis of the swamp man thought experiment (http://www.cyberschnauzer.com/writing/swampman.htm)