Trolleys and Double Effect in Experimental Ethics

Abstract

In one of analytic philosophy’s infamous thought experiments, a runaway trolley is about to kill five workmen who cannot move off the tracks quickly enough; their only chance is for a bystander to flip a switch to divert the trolley onto a side-track, where one workman would be killed. In a parallel scenario, the bystander’s only chance to save the five is to push a fat man off a bridge onto the tracks: that will stop the trolley, but the fat man will die. Why is it permissible for the bystander to divert the trolley onto the one workman by pressing the switch while it is not permissible for the bystander to stop the trolley by pushing the fat man off the bridge? This is the so-called Trolley Problem, resulting from Judith Jarvis Thomson’s (1976; 1985) adaptation of an example from Philippa Foot (1967). If it is permissible to intervene in the so-called Bystander at the Switch scenario while it is not permissible to intervene in the so-called Fat Man scenario, then the Trolley Problem arises and we must explain the moral difference between these two cases. And if the results of Marc Hauser’s Moral Sense Test are to be believed, then according to public opinion it is indeed permissible to intervene in the former case (around 90 percent of respondents to the Moral Sense Test thought as much — Hauser, 2006, p. 139) while it is not permissible to intervene in the latter case (only around 10 percent of respondents thought it permissible to intervene).