Plank of Carneades

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In ethics, the plank of Carneades is a thought experiment first proposed by Carneades of Cyrene; it explores the concept of self-defense in relation to murder.

In the thought experiment, there are two shipwrecked sailors, A and B. They both see a plank that can only support one of them and both of them swim towards it. Sailor A gets to the plank first. Sailor B, who is going to drown, pushes A off and away from the plank and, thus, ultimately, causes A to drown. Sailor B gets on the plank and is later saved by a rescue team. The thought experiment poses the question of whether Sailor B can be tried for murder because if B had to kill A in order to live, then it would arguably be in self-defense.

[edit] Plank of Carneades in fiction

In the Kindaichi Case Files manga volume 6, The Legend of Lake Hiren, the target of the murderer was in a situation involving Carneades' Plank.
In the 2003 movie Saw, Doctor Gordon must kill Adam Faulkner in order to be released from a remote room. This situation could be argued as involving Carneades' Plank.
In the anime Gunbuster, Operation Carneades refers to a military exercise to destroy a large portion of the galactic core to insure mankind's survival at the expense of an alien menace.