But an objection springs to mind. Surely the [Roman Catholic] tradition accepted that one may rightly choose to kill, to destroy the life of a human being, for the sake of greater good, for example, to save a larger number of lives, or the life of a more important person?
Aquinas, for one, did not think so. In this context, as in all others, he firmly denies that one should seek to identify, and choose, "the lesser evil." Killing in self-defense, capital punishment, and public killings in war against external or internal enemies were none of them justified by him on any such ground. To show the possible justification of killing in self-defense, he used exclusively an analysis of action, distinguishing between intention and side effect. To argument for the possible justification of killing in the administration of justice, he contended (in effect) that such a killing need involve no choice to destroy a human good either as end or as means, but instead can be done with a different intentionality, that is, under a different description: restoring the order of justice violated by the one killed who, moreover, by his violation of justice, his fault, had removed himself from the dignity of the human. Here, I believe, Aquinas's explanation may be challenged. Still, his intent to avoid any explanation of the type which proportionalism uses and generalizes is very clear.
(John Finnis, Moral Absolutes: Tradition, Revision, and Truth [Washington, DC: The Catholic University of America Press, 1991], 55-7 [italics in original; footnotes omitted])
Note from KBJ: Finnis uses "proportionalism" rather than the more common term "consequentialism."
Keith Burgess-Jackson, J.D., Ph.D. 