Israel’s war in Gaza has once again proved what all just war theory scholars know: people only pay attention to just war theory after a war has begun. Still, recent discussions about the justice of Israel’s war are useful, even if belated.

Much of the conversation has centered on the question of proportionality. Andrew Sullivan, for example, writes that

You do not launch a just war if it leads to greater evils than the status quo ante. There must be reasonable proportion between means and ends.

Sullivan goes on to argue that, contra the requirements of the Catholic Catechism, Israel’s war creates more evil than anyone can reasonably expect it to alleviate. The American Prospect’s (decidedly non-Catholic and non-conservative) Ezra Klein echoes Sullivan’s concern, writing

There is nothing proportionate in this [Israel’s] response. No way to fit it into a larger strategy that leads towards eventual peace. No way to fool ourselves into believing that it will reduce bloodshed and stop terrorist attacks.

Commentary’s Noah Pollak rejects this assessment, arguing that Sullivan relies upon an obsolete understanding of proportionality. Pollak, following Michael J. Totten, suggests that the U.S. military’s Law of Armed Conflict provides a better definition of proportionality, namely that it “prohibits the use of any kind or degree of force that exceeds that needed to accomplish the military objective.” Given that Hamas is still firing rockets into Israel, Pollak says, clearly Israel has not used more force than is needed to accomplish the military objective, and hence the war passes the proportionality test.

For starters, we should note that Pollak’s argument is fatally flawed. The logic of the proportionality rule runs as follows:

If a nation uses force that exceeds that needed to accomplish its military objective, then that nation has failed to act in a way that is proportional.

Pollak denies the first half of the conditional in order to conclude that Israel falls within the bounds of proportionality. But, of course, that move commits the logical fallacy of denying the antecedent. Pollak’s argument requires that we read the proportionality rule as saying

A nation fails to act in a way that is proportional if and only if it uses force that exceeds that needed to accomplish its military objective.

It’s far from clear, however, that proportionality can be limited in this way. It’s not that hard to see why this rereading fails. Suppose, for example, that Israel set as its military objective the elimination of all terrorist acts emanating from Gaza. Accomplishing that goal might well require killing not just every current terrorist, but also every potential terrorist. In other words, wiping out every single resident of Gaza might well be the only way of accomplishing a particular military objective. The problem with such a reading, then, is that it makes our definition of proportionality contingent upon a nation’s military objective. But what are we to say when we want to describe a military objective itself as not proportional?

All this is not to say that the Sullivan/Klein line fares much better. Indeed, the entire discussion of proportionality is a red herring, one that confuses jus ad bellum with jus in bello. But that’s a subject for another post next week.