"To some people," Mgr. Ronald Knox wrote in 1945, "Hiroshima will have been a glimpse, unreasonable but not unaccountable, down that dark vista which opens before the mind if it thinks of a world without God."

Seventy-five years later, this seems to me still the most salient verdict upon the war crimes the United States committed against Japan. There are two distinct senses in which it is true. The first is simply that in the images of Hiroshima — the cloud of smoke that looks less like a mushroom than the bulbous head of a minotaur, the faces reduced to black leather with no eyeballs and hot red gashes where mouths should be — one sees what it means to believe that value-neutral laws of physics are sometimes unleashed upon unthinking matter. It is just atoms against atoms, hydrogen doing such and such to carbon.

The second, which follows effortlessly from the first, is that all the lofty-sounding nonsense talked and still being talked by philosophers and sages on the subject of morality is just that: qualia, memes, carbon impressions, acoustic phenomena. There is no such thing as an immoral particle or a wicked chemical reaction. The palace of wisdom is a castle made of sand (i.e., curious arrangements of silicon dioxide). In such a universe there can be no reasoning from first principles, or indeed principles of any kind. Even the frigid anti-logic of utility so often restored to by defenders of Truman (though curiously not by the man himself, who spoke bluntly of revenge) is meaningless in the face of such a reality. All of this is not just hinted at but shouted by the face of the alligator man.

The arguments have been made before. They will be made again with wearying frequency, repeated, not so much endorsed as mooed along with. Japanese civilians, we are told, weren't really civilians; unconditional surrender, rather than an innovation unheard of in the history of war between civilized nations, was a dictate of reason to which our enemies had no right not to submit; killing innocents actually saved lives. (The last of these arguments always ignores the fact that such casualty estimates were revised upward long after the fact for the explicit purpose of justifying the bombings on supposedly humanitarian grounds).

The arguments are also (except in the materialist universe Hiroshima invites us to inhabit) of no importance whatever. It would not matter if someone's bar-napkin purported to show that five or 500 times the number of American casualties would have been the result of a ground invasion. The deliberate targeting of civilians in warfare can never be justified.

This is why we cannot ignore the withdrawal of the United States from various arms control agreements. While any individual treaty can be open to criticism — particularly on the grounds that the agreed-upon enforcement mechanisms are insufficient — this administration's seeming indifference to the moral imperative of arms control cannot be passed over. Some of this ought to have been brought home by the recent explosion in Beirut, which was indeed initially mistaken by some observers for a nuclear detonation; this was a blast equivalent to some 300 tons of TNT, a fraction of the terrible power unleashed in Japan. Today's nuclear weapons are 3,000 times more powerful still.

Hence the actual vision with which, having shuddered and crossed ourselves, we should be left by Hiroshima, the one that should be its true legacy: a world without nuclear weapons.