"Moral agents sometimes have to act on the basis of beliefs
that are reasonable in the context but are in fact false. In
these circumstances, agents often act in ways that would be
right if their beliefs were true but that they would recognize
as wrong if they could see that their beliefs were false.
Sometimes our tendency is to think that what these agents do
is justified – for example, in the case discussed by Ferzan in
which one person, Defender, kills another, Threatener, who
has loaded one bullet into a revolver, spun the chambers,
pointed the gun at Defender’s head, and started to squeeze
the trigger.1 We think that Defender was justified in killing
even if we discover that the chamber was in fact empty. (Let
us refer to this as the ‘‘Roulette case.’’) We accept, however,
that if Apparent Defender had known with certainty that the
chamber was empty and that Apparent Threatener would (or
could) have pulled the trigger only once, it would have been
pointless and therefore wrong to kill her..."...