Only the foolish would allow themselves to be swayed solely by Jeremy Corbyn’s sincerity

The Assumption of Jeremy Corbyn oughtn’t to surprise. Not because the man himself has long been a flower in the Stop the War, Whoever Is Our Enemy Is Our Friend, And Never Mind Who That Means We Rub Shoulders With, daisy-chain-plaiting wing of the Labour Party, but because we couldn’t go on forever pretending that the coexistence of the soup kitchen and the banker’s bonus was just another of life’s unavoidable little cruelties. Once in a while we need the hard left to pipe up.

You don’t have to believe the electorate secretly hankers for a dose of Marxist-Leninism to accept that there are deep levels of justified bitterness out there waiting to be tapped. How Ed Miliband and his team of hopefuls managed not to tap them is a question still engrossing the Labour Party, but the idea that its socialism was to blame never was convincing, if only because it didn’t look or sound socialist. Maybe we’d forgotten what socialists are meant to look and sound like. Well, now we’ve been reminded. They’re meant to look and sound like Jeremy Corbyn.

I can’t pretend to know what draws anyone to a politician, never having been drawn to one myself, but it would seem that nostalgia has a lot to do with it in this instance. A rough beast we thought extinct has come slouching back out of the undergrowth.

As for those who are too young to remember him the first time round, they are astounded by the novelty of a politician who resembles a British Rail booking clerk moonlighting as a polytechnic sociologist, except that they won’t remember what British Rail or a polytechnic was. Such an alliance, between those with faded memories of CND and funded trips to the Soviet Union, and those with no memories of anything, is proving formidable. It offers to efface, at a stroke, the occasionally shoddy pragmatism we’ve grown accustomed to. The camp fires burn; our souls are clean; we clap along and anything feels possible.

I’m not against it. I like a singalong. And I’m a bit of a sentimentalist for the past myself. Just before the trains were handed over to Richard Branson they were almost running on time and selling sandwiches designed by Clement Freud and wines selected by Fay Weldon. Now they won’t tell you what platform any train is leaving from until it’s left and the food might have been prepared by Primark. So I’m with Corbyn on taking back the railways, no matter that he hasn’t yet named the novelist he’d like to see selecting the wine.

I’m with him on energy companies as well. Why shouldn’t the state make a profit out of heating my Jacuzzi? On protecting public libraries, too, I agree. Ditto not making the poor pay higher taxes than the rich. Ditto not burning the unemployed at stakes. If this makes me a socialist, then I’m a socialist. But here’s a question: why can’t we oppose the inequities of a society weighted in favour of wealth, and all the trash that wealth accumulates, without at the same time having to snuggle up to Putin, pal out with Hamas, and make apologies for extremists?

The sad collapse of Kids Company highlights the plight of neglected children; it’s a national disgrace that without such charities there is no one to pick up the pieces. We should be able to admit that and keep Trident. And bomb Isis in Syria. And look back on the IRA’s terror campaign with something less than misty-eyed affection.

Truth isn’t a carpet not a single thread of which dare be removed without the entire tapestry unravelling. In fact, the more individually brilliant the threads, the more exquisite the carpet. But the Corbyn catechism is predicated on the presence of a divine unsmiling artificer at the loom, weaving his single truth over and over again. The oppressor’s wrong, weave weave, the wickedness of the West, weave weave, imperialism, weave weave, and our own responsibility, weave weave, for every act of violence directed against us. The Great Banality Carpet woven on the Great Loom of the Single Thought.

Socialism has learnt from religion to keep all promises of salvation simple – no one ever yet lit a candle for nuance – and not to underestimate the allure of masochism. The faithful feel holiest when blaming themselves, except the young, who feel holiest when blaming the old. For all the wicked, colonialist things our parents did, O Lord – including the Balfour Declaration, whatever that was – we say sorry.

Corbyn’s distinction is to have held on to these articles of faith while all about him have been losing theirs. In an age of facing-both-ways, he doggedly faces in one direction only. That this makes him authentic I have no desire to question. But our weariness with the vacillations of insincere politicians is no reason to put our trust in the rigidities of a sincere one. History teaches that the road to horror is paved with sincere schemes for mankind’s amelioration.

We are fools for sincerity. “The poetry of a teenager in love,” writes the Shakespearean scholar Jonathan Bate, “is sincere: that is what makes it bad. The key to dramatic art is Insincerity.” The dramatist, he goes on, should only pretend to feel what he expresses; that way he can pretend to feel the opposite just as well. Politicians aren't writers. But we should value in a politician no less than in a writer the ability to feel variously, admit ambiguity, understand the equal attraction of opposing truths, and to know when to mistrust “truth” altogether. The case against Tony Blair is sometimes that he believed nothing, and sometimes that he believed too much. Whatever the rights and wrongs of the Iraq war, it was God, he said, who whispered to him to go in. What if he was sincere in this? Do you, who abhor that war, applaud his sincerity? Or would you rather he’d been more calculating?

One thing that war does teach: the rightness of a course of action cannot be decided by the authenticity of its advocates. We should think twice before we let sincerity be our lodestone.