But it is only with the advent of the new drugs that rationing becomes explicit. Viagra may be "only" pounds 4 a pill, but the cost of supplying it to everyone who thinks they may need it would bankrupt the NHS within months. And some of the medicines which offer the prospect of relief for common debilitating conditions such as arthritis and Alzheimer's will be considerably more expensive than this.
Who, then, is to decide who gets them and who does not? For the doctors' trade union, the BMA, as selfish and irresponsible a vested interest as the worst of the flying pickets in the 1970s, the answer is simple: doctors. For the BMA, the question of who should pick up the tab is equally simple: their members' employer, the taxpayer.
This cannot be right, and Mr Dobson is to be praised for being the first politician courageous enough to say so. No doctor likes having his or her judgement of a patient's "clinical need" pre-empted by a Secretary of State for Health, but every doctor must realise that there are practical constraints which prevent them doing everything they would ideally do for everyone.
Nor does Mr Dobson pretend that the ordering of priorities in the health service is anything other than a difficult, messy and morally compromised business. But his is the right way to proceed: to lay down guidelines as to who should have Viagra which allow doctors discretion in applying them. For the BMA to instruct its members to defy the Government by prescribing as much Viagra as they think is justified by "clinical need" until the guidelines take effect is the kind of gesture politics which got Arthur Scargill where he is today.
The BMA accuses Mr Dobson of taking advantage of popular prejudice about impotence as some kind of joke to ration Viagra. It would be in a much stronger position if its members did not routinely prescribe unnecessary antibiotics, sundry other placebos and high-cost branded drugs for trivial conditions. But just because impotence can be a serious medical condition does not mean a new treatment must be immediately and fully funded on demand.
Of course, the medical profession has an important argument. It would be quite wrong to lump Prozac, Viagra and anti-obesity pills under the heading "lifestyle drugs", as if these were simply the equivalent of "soma", the happy drug of Brave New World. Depression can be a real, disabling condition with physical causes; likewise impotence and obesity.
But the BMA would do us all a service if it engaged in serious and persuasive argument, either that NHS spending as a whole is too low, or that spending in some areas of the NHS was less important to the health of the nation than spending on Viagra.
Healthcare is already being rationed: let the doctors join a grown-up process of managing the compromises and trade-offs required, instead of engaging in acts of petty defiance of guidelines with which they do not agree.