Professor Jonathan Waxman wrote eloquently and angrily in this space last week about the “absurd and arrogant” decision by the National Institute for Health and Clinical Excellence, NICE, not to recommend health authorities to give four good new drugs to kidney cancer patients. He underlined our low spending on cancer, the shortcomings of the “quality of life” calculations that NICE makes, and the “paltry” sums saved by denying these particular treatments. These arguments, from a senior oncologist, have power and reason; it is hard to think of the anxiety and panic the decision will have spread through the ranks of those who were hoping for a lifeline, even if it turns out to be temporary.

But there is more to be said, on a wider front, about the question of National Health Service rationing. The renal cancer decision seems - from medical comments - to be a particularly bad one, and it may change. Many NICE rulings have done: from Glivec (leukaemia) to Lucentis (age-related blindness). But some of the lay comments and arguments about the decision have been far too simple, like that of Billy Bragg on Any Questions. Such purists condemn all rationing and refusal of expensive treatment, saying from high principle that the NHS must look after everyone, in every way that has been invented, and should always be funded to do so.

That isn't possible. It never will be. Medicine and surgery have advanced too far to make that Utopian universal guarantee viable, and so has society. We now classify as illnesses things that once were accepted as mere misfortune: infertility, addiction, old age, gloom, shyness or childish overexuberance, unusual physical appearance. In many ways this modern solicitousness is admirably humane; economically it is a nightmare. No budget can ever stretch to meet every need with the ideal and latest treatment.

So there is already rationing in the NHS. Oh yes, there is, and it isn't going to stop under any government. Some local health trusts won't give you a new knee if you're fat, or IVF if you smoke, or liver transplants if you drink. Others will. Some defy guidance and go for the latest cancer drugs, yet have woeful mental health services; some run model services for the elderly but refuse to countenance stomach stapling, or minor cosmetic procedures for patients tormented by their sticking-out ears. As to less visible decisions, GPs - now made strongly aware of economics by the fundholding system - make judgments every day: based on age, usefulness, even likeability.

If you read back over ten years, especially in medical journals, the same message keeps coming through: we have rationing, but it is bad rationing because it is muddled, irrational, inconsistent, and all too often covert. Nine years ago a survey of 3,000 doctors found that one in five had known a patient die or deteriorate rapidly because treatment couldn't be afforded. A senior BMA spokesman, Dr Hamish Meldrum, said: “We have to make choices and set priorities... people have been mucking around trying to avoid the word ‘rationing' but we would like a whole public debate.” Geographical anomalies were also striking.

Two years later the British Medical Association said that the concept of the NHS as a service offering all treatments may have “outlived its usefulness” because some rationing is inevitable. Six years later, again, another survey found that it was already half of all doctors - not a fifth any more - who admitted they had patients suffering because of cost. Again, that call for open debate. “Rationing,” said Dr Michael Dixon of the NHS Alliance, “is the great unspoken reality... the only people who refuse to mention the R-word are the media and the politicians”.

The BMA suggested last year that we make a clear statement of “core services” available nationally, leaving local health authorities able to decide, when they had spare money, on what to offer beyond the core: fertility treatment, stomach stapling, cosmetic adjustment, removing the sort of varicose veins that present no health threat. Their report also pleaded for some mechanism to protect the NHS from day-to-day politics, with an independent board taking power away from beleaguered and media-sensitive politicians. There are problems, certainly, not least the difficulty of deciding when local discretion becomes a resented “postcode lottery”. But the calls for a proper debate go on - depressingly identical over the years - right up to this year's BMA statement that rationing is “a fact of life” and we should be honest about it.

Governments freeze at the very idea. Who wants to be in charge - and facing the artfully heartbreaking media tales of deserving cases - at the moment when such rules are laid down? Let me pluck examples from the air, endorsing none in particular. Imagine yourself PM at the moment when it is firmly stated that IVF can't be funded because infertility is not life-threatening whereas cancer is; that drunkards, smokers and addicts are required to get clean before any but emergency treatment; that stomach-banding is subject to co-payment in arrears since you'll be eating less; or that life-extending (as opposed to palliative or Alzheimer's) treatments cease at 85? Imagine being the hard-hearted monster who rules that under-50s, breadwinners and parents of young families get formal priority with new cancer drugs, or that there is an age beyond which heart surgery is not offered. My mother, who died last week at 92 (in an excellent cottage hospital), famously turned down a pig's heart valve two years ago with the sharp observation that the idea was “unseemly'. Being from a morally robust wartime generation and reading The Times daily, she was aware of greater needs unmet.

As I say, I endorse no measure in particular, so don't write in. But the current system is no good: patchy, pot-luck, covert, giving shocks and alarums with every NICE ruling. I am all for doctors making clinical decisions; I am all for the NHS learning to waste less money on administration and duff computers. But as a nation we really do have to sit down and agree on what is in the core national entitlement, and what is not. There would still be more help, hope and comfort in that core than previous generations (and much of the present world) could dream of. And we would know where we are.

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