Why have children? It’s a question most parents would find difficult to answer, however much we love our kids. Because it just happened. Because it felt right. Because I just really wanted a baby. Significant decisions, changing the course of entire lives, are made in the dark. None of us truly deserves the role to which we have appointed ourselves. Our children, meanwhile, have no choice at all.

On this weekend’s Sunday Politics Iain Duncan Smith resurrected the idea of restricting child benefit to the first two children in a family. It would, he said, “help behavioural change”, by which it is assumed he means dissuading people from having children they cannot afford. Duncan Smith has four children; presumably this is okay because a family such as his would not be in receipt of child benefit anyhow. He has earned the right to reproduce; it appears the rest of us need further guidance.

I’ve always found child benefit a curious, manipulative kind of payment. It is symbolic insofar as it’s not enough to cover anything specific (the cost of giving up paid work, or of clothing and feeding a child), but it’s also very real. The money does make an actual difference. The Policy Exchange think tank claims that the arrival of a first child makes the biggest impact on family finances, but unless you are wealthy it can be the cumulative effect of having more children that cuts deepest (child benefit is lower for subsequent children already).

I don’t believe that withholding payments for third children would stop many parents from having a child if they wanted one; I don’t think Iain Duncan Smith does, either. Instead it’s a way of exploiting this mix of the symbolic and the real. Make some people suffer just that little bit more, but make it a judgment on them. Don’t come straight out and say “I don’t think poor people should breed” (since, after all, that probably isn’t what you think); just plant the idea in people’s minds that if some families are suffering, it’s because they selfishly chose to breed beyond their means.

Clearly, poverty in large families is a problem. It does not, however, follow from this that large, poor families are a problem, despite what George Osborne would have us think. Families for whom an extra £13.55 a week makes the difference between a debt spiral or muddling through aren’t the ones consuming the majority of resources. They aren’t destined for over-paid jobs in which they ruin the lives of others while continuing to take home bonuses for nothing at all. Instead they’re already lined up to do the jobs none of the governing classes want their children to do, on zero-hours contracts or for jobseeker’s allowance alone. Making their early lives more difficult won’t stop them existing; it might, however, make them that bit more hopeless and crushed. Maybe that’s the lesson IDS wants to teach? Some people are surplus to requirements, so worthless we won’t even make a nominal contribution to their upkeep. What can you dare to expect from life when the government thinks you shouldn’t have been born?

There are things that could and should be done to improve the lives of children whose parents “can’t afford” to have them. Offer a living wage. Ensure absent parents pay maintenance. Keep vital support networks up and running. Oh, but that’s all too hard and besides, why do it when it’s for people you don’t even like? It sounds trite to say that this government hates the poor but that triteness may be the only thing holding us back from unbridled outrage. There is an attempt to present children born in poverty, not as people, but as a parental indulgence, like mobile phones or satellite TV. The nudge-nudge messaging of IDS encourages us to resent parents for their offspring’s existence, at least until the children themselves reach that age – 14, 13, 12 – when it becomes acceptable to pass on the hate straight to them. What a great way for the privileged to absolve themselves of all the guilt they deserve to feel.

Selfish people will always play upon the fact that no parent has children for selfless reasons. It’s hard for any of us to say precisely why we do it, but I doubt any individual decision comes down to “for the continuance of the species and to care for an ageing population.” Some people put off having children until they have a certain level of financial stability, while others – perhaps knowing that this stability may never be offered to them – simply take the plunge. Others still don’t really make a choice; it happens and there’s no great, mystical way of saying whether it is the right or wrong time. But no birth is a mistake and no one is surplus to requirements.

If “behavioural change” is needed, surely it’s in the behaviour of those who perpetuate wealth inequalities while seeing no need to restrict the size of their own resource-guzzling families. Whether or not changes are made to the child benefit system, babies will continue to be born into poverty and for that, Iain Duncan Smith, you should feel ashamed.