Abstract
Deontologists hold that killing is so morally serious that it ought not to be done, even to prevent more killings. For such a constraint to matter, it must be that we should generally want it to be respected. That is, we should prefer Five Killings over One Killing to Prevent Five. But this verdict turns out to be incompatible with regarding it as a matter of great importance whether or not such a prevention attempt turns out to be successful. Since deontic constraints are incompatible with taking their violations seriously, we must reject them.