Research Article

Double Effect, Triple Effect and the Trolley Problem: Squaring the Circle in Looping Cases


a1 University College London m.otsuka@ucl.ac.uk

In the Trolley Case (Figure 1), as devised by Philippa Foot and modified by Judith Jarvis Thomson, a runaway trolley (i.e. tram) is headed down a main track and will hit and kill five unless you divert it onto a side track, where it will hit and kill one.


This is a revised version of a paper presented at an ‘Author Meets Critics’ session on Frances Kamm's Intricate Ethics (New York, 2006) at the Pacific Division Meeting of the American Philosophical Association in San Francisco in April 2007. It was also presented at the LSE Philosophy Department, the University of Manchester Centre for Political Theory, and as a James Martin Advanced Research Seminar at the University of Oxford, and I thank the members of these audiences for their comments. I'm grateful to Derek Parfit for email correspondences that prompted this paper. I also thank Frances Kamm, Gerald Lang, G. A. Cohen, Horacio Spector and Alex Voorhoeve for their comments.