Problem in ethics posed by the English philosopher Philippa Foot in her ‘The Problem of Abortion and the Doctrine of the Double Effect’ (Oxford Review, 1967). A runaway train or trolley comes to a branch in the track. One person is working on one branch, and five on the other, and the trolley will kill anyone working on the branch it enters. Clearly, to most thinkers, the driver should steer for the less populated branch. But now suppose that, left to itself, it will go to the branch with five people on it, and you as a bystander can interfere, altering the points so that it veers towards the other. Is it right, or obligatory, or even permissible for you to do this, thereby apparently involving yourself in responsibility for the death of the one person? After all, whom have you wronged if you leave it to go its own way? The situation is structurally similar to others in which utilitarian reasoning seems to lead to one course of action, but a person's integrity or principles may oppose it. See also acts/omissions doctrine; double effect, principle of.