It has never been easy to justify making people pay for something they don't use. That is often how disgruntled Britons now see the NHS and BBC, despite the fact that often those who complain about their high taxes or the licence fee conveniently forget their recent trip to their GP, the maternity ward or the hours they spend enjoying commercial-free TV and radio. But the greatest value of these last major publicly owned institutions is not even quantifiable and it is the consistent failure to make this most difficult of cases for the defence that leaves them so vulnerable.

There is a lot to moan about at the moment. We can gripe about crime and bad schools or the Olympics bringing London to standstill or corrupt and elitist politicians – a dog even won Britain's Got Talent. But there are still a few things that make me relatively pleased to live here. Two things, in fact. The poor raggedy old NHS and the bloated, sometimes crappy but often wonderful BBC. The reasons for lumping these two behemoths together is simple: they both contribute to something well beyond their material value and they are both under dire threat.

Sometimes it seems as if the forces of free-market conservatism are out to get the NHS and BBC precisely because their true worth cannot be expressed on a balance sheet. They are the unfinished business of Thatcherite reform. It's as if it is not just that the government wants to dismantle the NHS for the benefit of profiteering healthcare firms and the BBC for their media-mogul friends, but that it simply can't stand the idea of people contributing to a communal pot for the benefit of everyone. It must really get up the noses of Boris Johnson, who called for a Tory director general this week, and Andrew Lansley, who has fewer friends in public health than the MRSA superbug, to see people “wasting” their money on obscure radio stations and someone else's heart op.

What the NHS and BBC embody and promote is that most slippery and seemingly useless political trope - the public good. This makes it even easier for their opponents. That the mayor of London, not exactly unencumbered by friends in the media, thinks he has the right to meddle in the affairs of the BBC shows the danger it is in. That, after labelling nurses and doctors as communists, the health secretary can this week effectively accuse the Royal College of Nursing of lying over job cuts again demonstrates the way opposition to NHS privitisation is portrayed as wrong economically and ideologically. So in both cases, the fight to save the head and heart of the nation should not only employ facts and figures, but the abstract. Sharing, redistribution, pluralism, protecting the less able and serving the less resourced - these are not worthless because they cannot be rendered statistically. The issue goes far beyond ratings for Eastenders and Radio 3 or cancer recovery rates and waiting times for hip replacements.

It is logical for me to pay for a local radio station that I don't listen to because it serves a community in a way a commercial one never could - or a national network I don't like because it enriches our culture in a way a profit-seeking company would never have the freedom to. I don't need to benefit directly or even “see” the benefit in others, because I am already benefiting by living in a society where such things exist. In the health service the advantages are even more blatant. By contributing to the cost of healthcare for the poorest in society, the wealthiest are helping to reduce suffering in others and by extension for everyone. The social benefits of better universal health, more workers and less crime for example, are obvious, but an explanation involves the kind of conceptual thinking politicians do not trust themselves to present to the public.

The enormous cost of the NHS and the BBC and the way the funds are collected from the public are being used as a hammer to provoke the basest reflexes of self-interest and insularity, Preying on the short-termism and anxiety of recession, the enemies of public ownership are seeking to create an environment in which such ideals are seen as redundant and archaic. It doesn't help that the BBC is guilty of grandiloquent and budget busting projects, yet turns to cutting local and specialist radio – perhaps the greatest expression of its public service – to save money. Despite the faults and weaknesses of both institutions, the forces against them should be resisted. The NHS and BBC, flawed as they are, are not merely worth protecting, they are just about the only two things left that preserve any sense of national community and cohesion.

The mere act of public funding has value. It is not selfless charity or waste; providing our hard-earned wages for something not solely for our own good contributes to our own good because the world we live is a kinder, better, less dumb, less rapacious place for it. In other words, if you think Britain is a divided, violent, parochial and unenlightened country to live in now, without the NHS and the BBC it would be immeasurably worse. There's the rub: the NHS and the BBC make Britain a better place to live - immeasurably.

George Chesterton blogs on politics and culture for the Huffington Post UK