David Elstein is as ever, brilliant at shooting holes in other people's arguments. And his claims about the commercialisation of the BBC are sadly all too accurate. But that is the very problem we must address in practice.

Anyone familiar with the pathetic fate of public service broadcasting in the USA would see a perpetual diet of largely safe programming, funded by relentless appeals to the audience to keep them alive. Although they have a small audience, and are so badly structured as separate stations they have nothing quite like a network, they still are seen as some kind of threat by politicians who still try from time to time to abolish them.

It is impossible to share Elstein's sanguine rejection of seperately funded - and committed - public service structures as the only way to get many of the programmes needed to keep a proper spectrum of political and cultural output available on the air.

The so-called learning channels on cable and the occasional efforts at factual stuff by commercial broadcasters are anodyne and glossy formulaic info-tainment, and themselves are drops in the ocean.

They do nothing to sustain a culture of risk and creativity, of innovation, the very qualities we value in literature, print, on the walls of museums and concert halls, and in our own discourse. On most commercial channels, they are entirely ratings driven, and are shameful parodies of seriously committed investigations or other kinds of documentaries that used to be backed by commercial television in the UK at least.

Moreover, the few islands of good programming on commercial channels are often dispensed with whenever commercial pressures dictate it - like the death of World In Action, and Elstein's own programme This Week.

Our concern must be to find a way to protect the BBC and C4 from going the same way. Elstein rightly says that we are being offered more of the same on C4 and the BBC as on commercial channels undermines the case for protected funding - but not for doing away with the existence of the BBC or C4. They need to be encouraged, urged - indeed required - to adhere to the principles which allow them their special place.