I have been working on a long piece about the ideas of Herbert Gintis for the Guardian, and there are some bits left over after I rolled it al out and cut it to fit the tin.

The broader message of Gintis is that there can't be libertarian welfare states. If they are socially liberal, in the sense that people are allowed to boink as they please, then they will also be compulsorily liberal and preachers of intolerance will be threatened with jail. The impulses behind generosity are tied up with reverence for society's conventions both because they arose, in Gintis' scheme, from "the internalisation of norms" and because convention is a marker of belonging, and of playing by the rules. We need those markers to know that the recipients of our generosity will not take advantage of us.

Now, you can have narrow and conventional societies without welfare or kindness. But what you can't have is a lasting welfare state without a shared moral code and an agreement that this is important and exacting. This is the half-truth that people like Digby Anderson have got right.

This is not quite the same as shared values because liberals tend to talk about values as if they were the product of rational deliberation, which they are not. Values – in the strictly literal sense of a common sense of what it desirable and undesirable – come long before liberal rationality, which requires a long and specialised education. There are plenty of societies and subcultures without the faintest trace of liberal rationality, but none without some common values.

Society, in any rich and interesting sense, breaks down once everything, or even most things, are permitted. Digby, of course, supposes that his is the only moral code that will do the job of keeping society together. This is false. I knew him, and liked him in the early Eighties, but our friendship was an early casualty of aids. He was complaining that all the social workers whinged about "stigma" and said it was wrong to stigmatise people. What's wrong with stigma? He asked. Stigma and shame are things that all societies need. And I thought this was a disgusting way to treat the dying. On the other hand, I think he was quite right about the general point. Societies do need these mechanisms, and they will all develop them.

Various interesting spinoffs come from this idea. The most notable is the degree to which the idea of "choice" threatens state provision. It's not just that if people are free to choose private provision, they may do so. That, you can argue, keeps state provision up to the mark. This does sometimes work. You could certainly argue that the BBC is better because of ITV. But that is because the BBC is still to some extent a matter of national pride and the more channels there are, the less sense the BBC makes. But too much choice does damage national institutions, because it makes it obvious that some people are not paying their fair share. And if other people get away with that, why shouldn't we? This is, in Gintis' schema, as in real life, a very corrosive question.