If we don’t hold a firm understanding of why civilians should be treated differently than combatants, we can end up in indefensible positions. I see no way to interpret Rosenbaum’s comment except to mean that we should have no sympathy for children who are killed if their parents were Hamas loyalists. That’s a disgusting sentiment.

The just-war tradition of thought treats civilians differently in that just military action can never be designed to kill them. Their killing can only be tolerated, in that tradition, as an unintended byproduct of military action — and that evil can be tolerated only if the military action is likely to accomplish a good proportional to it. (It may be that Morris, his infelicitous phrasing aside, doesn’t intend any inconsistency with that tradition. Other remarks in his op-ed suggest that he merely means that Israel should be willing to tolerate more Palestinian civilian casualties, rather than that it should welcome more of them.)

This intellectual tradition isn’t based on sentimentality about civilians. Its conclusions don’t turn on any judgment of civilians’ political or moral beliefs, which in many cases may be odious. Civilians may even be complicit in some sense in the evils of war — for instance, by voting in a war-making government. Yet they’re noncombatants because they’re not involved in warfighting in any direct way, and their killing can’t be justified as an extension of the principle of self-defense.