Hobbes and Rousseau must be spinning in their graves at the news that Tony Blair is planning a "new social contract". The old idea of a social contract was that individuals exist in an implied bargain with the state: they'll play by its rules, and it will guarantee their liberties. What, by contrast, is the flavour of the new contract? Well, according to the new policy review that Blair has initiated, it goes like this. You'll only get a hip replacement if you promise to keep your weight down. Or, as a parent, you'll have to promise to do certain things at home in order to have your child educated at school. If you want stuff, you had better do what they say in return.

We have, of course, already paid for the public services that this newfangled scheme threatens to withdraw, which might previously have been thought "contract" enough. But let's try to imagine how such ludicrous-sounding stipulations might work in practice. If a woman gets a hip replacement and then fails to lose the required number of kilos, will a doctor perform a revenge surgery to remove the hip? Or maybe he'll just say: "Sorry love, you were warned. I'm not treating fatties any more."

This almost comically bad idea shows that, in the decadent coda of his career, Blair has snapped utterly free of the notion that government exists at the sufferance of the people. Not a man ever to have taken seriously the idea that he is a public servant, he has now morphed decisively into a kind of giant inflatable Mary Poppins, minus the joie de vivre, floating untethered in the sky above us all. Tetchily nannyish, he says to himself: all the problems of British society could be solved if the people would just - well, behave.