A Puzzle About Proportionality

The paper addresses a puzzle about the proportionality requirement on self-defense due to L. Alexander. Indirectly the puzzle is also relevant to the proportionality requirement on punishment, insofar as the right to punish is derived from the right to self-defense. Alexander argues that there is no proportionality requirement on either self-defense or punishment, as long as the aggressor/offender has been forewarned of the risk of a disproportional response. To support his position Alexander appeals to some puzzle cases, challenging us to explain why the requirement applies in some of them when it clearly does not in others. The paper responds to his challenge by answering two questions: why does the proportionality requirement exist in the first place, and when does it apply? The paper argues that the requirement holds because of our need to protect our rights from violation, and that it applies to cases where the person defending his rights counts as having imposed a cost on one of the offender’s options. An account is offered of when such cost imposition occurs.