Aggregation of Small Harms and Proportionality in Defense

Aggregation of Small Harms and Proportionality in Defense
Speaker: Jeff McMahan # Rutgers
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Date and Time
21st Feb 2014 16:10 - 21st Feb 2014 18:00
Room 1.20, Dugald Stewart Building, Edinburgh University

To reserve a place, please go to:

Professor McMahan is an internationally acclaimed scholar in the areas of global justice, moral philosophy and the ethics of armed conflict.  He is the author of over a hundred and twenty scholarly articles and two of the most important monographs in the field: Killing in War (Oxford: Clarendon Press, 2009) and The Ethics of Killing: Problems at the Margins of Life (New York and Oxford: Oxford University Press, 2002).

His talk at Edinburgh University will address the issue of proportionality of defensive force. In particular, when, if ever, might a person who inflicts a small harm on a large number of people be liable to be killed in defence of those people?  This question has important implications for the ethics of individual self-defence and the ethics of killing in war.

Those interested in having dinner with the speaker after the event should contact to reserve a place by 19 February 2014.


In the literature on “moral mathematics,” one issue is whether, and if so to what extent, it is wrong to cause a tiny harm to each of a large number of people, and in particular whether doing so could ever be as seriously wrong as causing a substantial harm to one person.  My topic in this talk will be the closely related issue of proportionality in defense against those who would inflict only tiny harms.  For example, might a person who would otherwise inflict a tiny harm on each of a large number of people be liable to be killed in defense of those people?  I will suggest that such a person seems liable to be killed in some cases but not in others, depending on what other people might be doing or on other facts about the context in which the harms would occur.  I will review a range of examples involving the infliction of tiny harms that reveal some surprising facts about the conditions and limits of liability to defensive harm.