Once we were citizens, now we are consumers. The BBC no longer knows its audience

One of the BBC's most ingrained characteristics is what might be called its reflexiveness: its habit – rather like one of those vast mythological creatures from the realms of Tolkienesque fantasy – of feeding off its own extremities. The symptoms may be as varied as the habit of commissioning some high-profile presenter to front a documentary for which his only qualification is the celebrity that comes with working at Broadcasting House, or making a lavish documentary about how the corporation "does" some particular event or spectacle, but the underlying condition is the same: a conviction that its importance to the taxpayer is such that it is entitled to spend the taxpayer's money addressing the highly compelling subject of itself.

Happily there are times when what can sometimes look like sheer vanity turns, imperceptibly, into something a great deal more fruitful. Last night, for example, Radio 4 broadcast a fascinating Archive on 4 programme under the title "Imagining the Audience". The audience in question turned out to be the original listeners of the Reith-era 1920s and 1930s, tuning in on their crystal sets to such highlights as Variety Bandbox and the hoe-in-hand musings of "Mr Middleton", the first radio gardener.

But nostalgia this mysteriously was not. For in a week where the Labour Party declared that it wouldn't "necessarily" be in favour of retaining the licence fee and fierce debates attended the prospect of a new chair of the BBC Trust, nothing could have been more timely than Matthew Sweet's enquiry into who exactly the first of the corporation's broadcasters thought they were transmitting to, and what this unseen constituency may have wanted from the medium now making its presence felt in their living rooms.

The relevance lay in its gradual uncovering of what Lord Reith and his henchmen and women believed to be their fundamental purpose: to entertain, certainly – cue on-air ballroom-dancing lessons, with accompanying diagrams in the Radio Times – but also to instruct and, just occasionally, to edify. Popular history tends to magnify the stereotype of the first BBC presenters as dandified exquisites in evening suits staring snootily down on packed humanity from their eminence on Savoy Hill, but the archive clips brought out and analysed by Sweet and his interviewees were almost painfully sincere.

This, clearly, was an organisation animated by a sense of responsibility to its listeners, and the media historian Jean Seaton could be found congratulating the Reith-era corporation for having the courage to "imagine its audience as citizens" – not talking down to them, or passively reflecting what came up from below, but assuming that there was some collective principle involved that might even be characterised as an ideal.

"Imagining the Audience" sailed home to port in the late 1930s, shortly before the point at which the bond forged between corporation and licence-holder grew tighter still and the war-time broadcasts of JB Priestley became so popular that Churchill, his vanity stirred, tried to have him taken off air. Hanging in the ether above it was another question which no modern BBC grandee ever feels in the least like answering. What kind of people does the corporation imagine its audience to consist of today, and what sort of things does it think that they might want?

Is it there to entertain, or is there a mission beyond churning out the kind of suet that can be found nightly on two or three dozen other channels? And in strict political terms, should an incoming Labour government conclude that current licence fee levels are unsustainable, then how exactly is it going to defend itself?

Naturally, the answers tend to vary from medium to medium and channel to channel. The part of the BBC which feels most confident of its role these days is probably Radio 4, which, as you might imagine, is constantly criticised for being a middle-class pleasure-ground full of people with educated accents discussing topics which are only of interest to anyone earning £40,000 a year.

Over in Television Centre, on the other hand, a much less roseate picture emerges. The prevailing spirit of BBC One, for example, always seems to me to be one of simple terror: the terror of being accused of talking down to its audience, the fear of offering anything remotely "difficult" to cowed and presumably dim-witted viewers, the awful consequences of not being consistently "entertaining". This tendency is especially noticeable in news broadcasting, where several of the correspondents are not much more than comic turns and one yearns for an old-fashioned BBC "expert" – even one in an evening suit – who can say what has to be said without exaggerated hand-gestures or putting the stress on all the wrong syllables.

None of this, though, gets us any closer to the identity of that tantalising abstract, the specimen viewer. Who is he or she? Where does he live, and what does he want? To judge from the afternoon schedules, the BBC One and Two viewer is your average Daily Mail-reading hedonist, avid to improve or transfer from the piece of real estate on which he proudly squats, keen on antiques, tethered to kitchen or garden or, alternatively, off to some exotic holiday destination where it never rains and all the natives are friendly.

As for "young people", a part of the demographic about which the corporation became famously neurotic in the 1990s, they seem to be exclusively quartered on BBC Three. "Culture", when not defined in strict celebrity-actor, classic serial terms, is almost entirely confined to the wonderful BBC Four, where there is, alas, no money and one's pleasure in individual programmes is invariably tempered by the knowledge that they will be repeated three or four times in the coming months.

Little of this inspires confidence in the discriminating viewer. In fact this one, if given a free hand, would simply jettison BBC Two altogether and give the money to BBC Four which, as far as one can make out, is performing precisely the role that Two was engaged upon 30 years ago. Where the corporation excels, on the other hand, is in any kind of public spectacle or national event. Give the BBC a general election, an Olympics, a military anniversary or a royal funeral and – last year's Diamond Jubilee disaster notwithstanding – its sense of savoir faire, of existing merely to fulfil the august function that is now demanded of it, instantly returns. No doubt the idea that the UK is a coherent national entity is one of the great modern myths, but watching David Dimbleby preside over a strew of election results, or the coverage of last week's D-Day commemorations somehow sustains the illusion of us all being in this together.

And this, you suspect, is the closest the modern BBC comes to that Edenic idea of the licence-payer not as some hyper-critical and occasionally vengeful consumer but as "citizen". Inevitably, notions of public broadcasting have moved on in the 80 years since George Bernard Shaw was enticed on to the airwaves to give the nation's sixth-formers his views on "literature", and one would prefer that Lord Reith stay unmolested in his grave.

All the same, the next time the corporation embarks on a bout of soul-searching, it might start by remembering that we are not worker ants who buy things, or cook things, or have a desperate need to feel good about ourselves, but that there are collective and even spiritual interests and responsibilities at stake, and that none of them automatically relies on what, in modern TV-land, passes for entertainment.