Howard Jacobson: I've suddenly grown interested in Clare Short

Remember Hector in Shakespeare's Troilus and Cressida? Did ever man marshal more persuasively the arguments for peace? Reporting that the Greeks have made again their offer to end this "cormorant war" and let bygones be bygones so long as Helen is returned, Priam, King of Troy, turns to the noblest and most clear-headed of his sons.

"After so many hours, lives, speeches spent ... Hector, what say you to't?" And Hector says his say, searching "to the bottom of the worst", reminding his brothers of the uncertain outcome of the combat, calling into question the honour of the cause, citing Aristotle – a remarkable act of prescience in itself since Aristotle wasn't born yet – and shaking his head at last over Helen's value, both as a prize and in herself. "Brother, she is not worth what she doth cost the keeping."

A judgement of such exquisitely measured finality, laced with such sweet fraternal regret – a verdict delivered more in sorrow than in anger, and possessed of more understanding of the causes that make men violent than we usually find in those who sue for peace – that we do not doubt its justice. A man cannot be in error who cadences his thoughts so feelingly.

And yet, before the scene is out, Hector has turned tail on his objections, inclined to the will of his "spritely brethren", resolved to fight to keep Helen, and found dignity in the cause he'd torn to shreds. Remind you of anyone?

I do not myself join those who censure Clare Short. Though I have never previously found myself drawn to her or what she stands for – not caring for people who wear their hearts on their sleeves or enact their consciences in public – I am suddenly grown interested in her now that she is accused of not standing for anything at all. Whether it is she who helps me to understand Hector's moral somersault or Hector who helps me to understand hers, I cannot decide. Let's say they help me with each other. Certainly it should be harder now, anyway, with the example of the Minister for Overseas Development before them, for critics baffled by Hector's tergiversations to accuse Shakespeare of poor characterisation.

As for what to make of such changes of heart, Coleridge's theory of polarities might be useful: his detection of a moral law under whose governance things pass into their opposites and contrarieties change places. Whether it is indeed a moral law or just some slipperiness at the centre, a beneficent fault-line running through our natures and the languages we speak, I am not philosopher enough to know. But the evidence of it should make us hesitate before returning to what we enjoy doing best – running headlong into denunciations of one another's faintheartedness and folly.

It would seem sometimes to be the case, at any rate, that no sooner are we touched by the extremity of truth in one position than we proceed, almost by force of nature – as though morality itself turns like a wheel – to embrace the truth, or other counter-inducements, inherent in its opposite.

At such moments people who want principle to be steadfast tear their hair. But what if nature turns her wheel to intelligent purpose, knowing that it is of the greatest good that some among us are not the victims of obdurate resolution, but are capable of occupying contradictory positions and finding their enemies in themselves?

If you ask me what this greatest good might be, to the promotion of which nature turns her wheel, here is my best shot: not to acknowledge a logic of change and alteration at the moment of maximum attachment to our convictions or beliefs is to be left high and dry in extremism. Thus a fundamentalist – someone who is incapable of embracing his opposite.

When stubbornness rules, I am not sorry to feel the ground beneath us lurch and words change places with their antonyms. Was Clare Short right to accuse Blair of "recklessness" when he might just as well have been charged with overcaution, with trying altogether too hard to secure legitimacy when that minx legitimacy was hiding and refusing to come out? Was it reckless of him to have been so cautious? And is it not cautious of him now to be so reckless, accepting for a moment the future threat he sees in Saddam's unaccounted arsenal? Rash today in order to be safe tomorrow.

Meanings slip and slide, unless you are fanatic.

Of the other paired opposites we dread or welcome in the present conflict, there is one I believe we have a duty to resist. Not because I pick and choose where I think the wheel should stop, but because this one is punitive, akin to dramatic irony, a theatrical cruelty of man's making, not nature's. Satisfaction in the quid pro quo of terror is what I'm talking about. The prediction that a war waged, supposedly, to crush terror, will ironically engender more of it.

How shapely, that is, if you oppose the war with a single mind and undivided heart. And how chilling, because like all prophecies it half invites the thing it warns against. "Cry, Troyans, cry," shrieks the mad Cassandra. "Let us pay betimes/ A moiety of that mass of moan to come." Not polarity with its calming equilibrium, but comeuppance.

Let them say so outright then, the comeuppance merchants. Let them openly wish the worst on us, rejoice as many half did on 11 September. Otherwise make the case, say it loud, say it everywhere, say it all the time, that whatever else the madcaps of the western world are doing, they are not waging a war against a people and a faith, would not be so deranged as to try it even if they had a mind to, which they do not. Number the wrongs if you will, number them till you run out of fingers and toes, but do not allow falsities to proliferate simply because you wish to say I told you so. Whoever says "it will be perceived this way" is complicit in its being so.