Man bites dog is a fundamental law of journalism. Every wet-behind-the-ears junior reporter knows 'dog bites man' is not news because it happens every day.
Man bites dog, however, is enough to get the editor of the Back Street Bugle hurling his green eye shades across the room before yelling "hold the front page!" and furiously thumping his ancient typewriter,
The news-consuming public understand the man bites dog rule. That's why the stories most typically shared are (using Sunday's BBC website as a random example), "Man did not notice nail in brain"; "Scotland's secret artist mystery"; and "Schoolgirl sailor triumphs after battle with authorities". In other words, the surprising, unusual or bizarre.
Politicians, though, disobey the man bites dog rule. They take something outrageous and exceptional and use it to suggest a pervasive rottenness. Britain is broken, young people are feral monsters, and anyone claiming benefits is likely to be a scrounger, a cheat or a rogue.
Just look at the evidence, they cry. Work and pensions secretary Iain Duncan Smith, fulminating against turbulent priests at the weekend in good Thatcher-era style, spluttered that there are people living in expensive houses claiming unemployment benefits.
Shouldn't the moralising bishops be more worried about Joe Taxpayer and working families who are 'doing the right thing'? (Claiming benefits you're entitled to, in Mr Duncan Smith's book, would seem not to be the right thing at all).
Well, it wasn't that long ago that ministers were pointing to the fact that some people were getting more than £100,000 in housing benefit as evidence that the system was rotten. As it turned out there were about five of them. And that's in the context of 4.92m people claiming housing benefit across the UK, financed by just under 30m taxpayers.
Politicians have always spiced up their speeches with anecdotes and examples, There's nothing wrong with that. But it becomes mendacious when an exceptional or exaggerated example is used to infer a generality. Remember Theresa May and the illegal immigrant allowed to stay because of his cat? She wasn't making it up, she said. Except of course someone did make it up, and she repeated it.
Or take last week's pseudo-story about migrants, touted by two government ministers as evidence of a scandal because 371,000 people not born in the UK claimed out-of-work benefits at some point last year. It turned out that 98% of these claims were almost certainly legitimate.
In a big system - and it's hard to find one bigger than the tax and benefits system, which one way or another affects us all - there will always be abuses or anomalies, and the raw numbers will look quite large when you take them out of context.
But to argue that this requires a reform of the whole or justifies arbitrary cuts, such as the £26,000 cap currently proposed, is specious. It's like pretending we live in a world where men routinely go around biting dogs.
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