This thought experiment comes from Bernard Williams.
Context for this thought experiment surrounds the different schools of thought regarding ethics and ethical theory. One school of thought is consequentialism. Consequentialiam, as the name implies, says we should always to whatever produces the best consequences. Another school of thought is contractarianism. Contractarianism says we must adhere to moral rules and standards, even if breaking them may produce better consequences.
With some context added, this is Williams’ thought experiment:
Jim is travelling through South America. He enters a village where twenty men are being guarded by armed men. Pedro, the officer in charge, notices Jim and informs him of what is happening. Pedro says that the captives are a randomly selected group of inhabitants that are about to be shot to end recent acts of protest against the government. Pedro would like to honour Jim’s presence by having him shoot one of the villagers. Jim has the choice to refuse. However, if Jim does, Pedro will release the surviving nineteen villagers. If Jim does not, Pedro will shoot all of them.
If you were in Jim’s position, would you shoot one of the prisoners or would you not? And why or why not?