The argument that the bombing of Hiroshima was justified on the grounds that it is claimed that on a balance of probabilities it caused less suffering than would otherwise have occurred in a continuing war does involve a certain logic.

But it is a logic that has some very disturbing implications. It is a logic that says that, in certain circumstances, it is justifiable to do anything, without any limits whatsoever. The only thing that matters, in the last analysis, is that the ultimate good effects envisaged will outweigh the present suffering caused. And the people who have to make that judgement are those who carry the actions involved.

Before we accept that logic we should recognise that it is a logic shared with the people who engineered the atrocities associated with Al Qaeda, and even with the architects of the Holocaust.

If we believe Hiroshima was justifiable on those grounds, our argument with those kinds of people is reduced to one about weighing good and evil effects in the balance; and while that is an important argument, underlying it is a shared understanding of ethics, which is, if the sums work out right, there is absolutely nothing which is ruled out.

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As for Nagasaki, that wasn't anything to do with ending the war, it was essentially just a way of testing a different type of atom bomb. Even on the kind of logic I mentioned just now, it was unjustifiable, and should be recognised as a war crime in every sense.