WHY must every tragedy have a lesson? According to the Chancellor of the Exchequer, the brutal actions of Mick Philpott, a layabout father of 17 children, who accidentally killed six of his children in a moronic attempt to frame his mistress, shows that “there is a question about the welfare state... subsidising lifestyles like that.” Others have been less nuanced: the Daily Mail sparked the entire debate by branding Philpott a “vile product of the welfare state.” Behind all this is a particularly persistent Conservative idea: that welfare encourages feckless men and women to have lots of children to get benefits. In 1992, Peter Lilley, the then social security secretary, denounced (while singing) “young ladies who get pregnant just to jump the housing queue.” More recently, in October, Iain Duncan Smith, Mr Lilley’s latest successor, suggested limiting workless families’ access to child benefit and tax credits. And this morning, David Davis, a right-wing backbencher inexplicably treated as a political heavyweight, suggested taking away child benefit for all couples after the second child.

All this appeals to right-wingers. They argue that people perhaps shouldn’t have children they can’t afford, particularly when other people in work are having to delay starting families. Possibly, on moral grounds, they are right. But, pragmatically, it is simply not worth it.

To begin with, it is tackling a tiny problem. Though most of them seem to end up in newspapers, in 2011 there were just 130 families in the country with ten children claiming at least one out-of-work benefit. Only 8% of benefit claimants have three or more children. What evidence there is suggests that on average, unemployed people have similar numbers of children to employed people. So despite Tory fears, it is not clear at all that benefits are a significant incentive to have children.

To anyone who actually has an idea of what benefits are worth, it is obvious why. They are simply not generous enough. Universal child benefit for an additional child is just £13.40 per week. Child tax credit—which is claimed by those in work as well as out of it—can add up to another £50 or so per child, dependent on the family’s overall income. So that’s £63.40 per child, per week. Housing benefit will increase to cover the fact that children need space, but that all goes to the landlord.

Out of that £63.40 must come clothes, food, transport, entertainment, Christmas and birthday presents and everything else that a child needs. Only the most wicked Fagin-like parent is going to be able to extract very much money for his own enjoyment. And to discourage him from having children (which may not even be successful) you are punishing everyone who has a large family. They are not all irresponsible. Pity the woman who has twins shortly before her husband loses his job.

And what happens when parents can't afford to raise their children? Are unemployed women who get pregnant for a third or fourth time going to be strongly encouraged to get abortions, because they will not be able to afford to raise the child? If mothers literally cannot afford to clothe or feed their children, will they be taken into care? If not, who pays for the children to be fed? There are already reports of children turning up to school hungry in the poorer parts of the country.

That, presumably, is why Mr Davis and Mr Duncan Smith now only want to take away child benefit from bigger families, rather than all extra benefits. But if they honestly think that will be easy, they should consider what happened the last time the government tried to cut child benefit. There was an outcry, led by the Conservative-leaning newspapers, followed by a (partial) u-turn. And an awful lot of middle class families have three or four children too.

An unedited draft of this blog post was published earlier by mistake. It has now been amended.