If the past is another country, then it's time we renewed our passports

We cannot apprehend who we are now if we cultivate ignorance of how we were then

"The wrecking of British Intelligence," the headline screamed from the tabloid left open on the table of my favourite Soho tea rooms. Imagine my excitement. A pot of Lapsang Souchong, a dark chocolate éclair, and an acknowledgement of intellectual crisis on the comment page of the Daily Mail of all organs. Elsewhere that day I had read about the survey conducted to mark Words Worth Reading, an event, which I endorse with all my heart, in which 200,000 children from across the country will simultaneously recite "I Wandered Lonely as a Cloud".

In a nutshell, what the survey unearthed was that most people under 40 wouldn't know a Wordsworthian daffodil from a dishcloth, and still less would they know the line of any poem that wasn't written by Ricky Gervais. As for nutshells, they would no more be able to tell you who said he could be bounded in a nutshell and count himself a king of infinite space, than they would know that Hamlet wasn't only something you smoked. The wrecking of British Intelligence indeed!

Except that, as it turned out, the Mail wasn't referring to that sort of intelligence at all. It meant the other sort - spying, gathering secret information, finding weapons of mass destruction where there aren't any, blah blah.

Don't get me wrong: I have the highest regard for people who do such work. Whenever I meet a person I find truly interesting, well travelled, sophisticated, a man or woman who takes fortune's buffets and rewards with equal thanks, a man or woman who is not passion's slave, I immediately assume he or she must be a spy.

Particularly she. The love of my life, when I was 17, though she was working behind the baby-food counter in Boots when I met her, turned out to be a spy. That's what she told me when she left me, anyway. This is a far, far better thing, she said. There is some corner of a foreign field. I will arise and go now. Sunt lacrimae rerum. There is a world elsewhere.

So I am not one who needs persuading of the importance of intelligence in the investigative meaning of the word. But what are our spies and secret agents defending if not the value we place on intelligence of the other sort, the cultural memory we bear, the inward eye (both individual and national, for nations too have eyes) on which flashes, in vacant or in pensive mood, not only Wordsworth's golden daffodils, but Tintern Abbey, the creeks and bays of Cumbria's rocky limits, those reprimands of Nature which shaped his imagination and made the boy a man. Our spiritual inheritance.

Yes, I know that intelligence is a faculty more active than mere knowing and remembering. But there can be no active intelligence that does not call upon a store both of recollection and of knowledge. Nor is acquaintance with what was once quaintly called "the best that has been thought and said" a merely passive or nostalgic state. It doesn't matter whether or not people know (as 91 per cent of those surveyed did not) that it was Oscar Wilde who said "I can resist everything except temptation", partly because it's not that interesting a thought. Nor does it matter if our heads are busy, just this minute, with the sayings of David Brent. But it does matter if we are so besotted with the present and the near that we have ears for nothing and for nowhere else.

There is an extremely touching tribute from a father to a son in the winter issue of Modern Painters, an art magazine with which I am associated, though I know neither the father, Denys Lasdun, architect of the National Theatre, nor the son, the poet James Lasdun. Among the many reminiscences which strike me in the article is one in which James Lasdun attempts to define a particular quality of receptiveness and excitability in his father, "a thrillability, I want to call it - that I associate almost exclusively with people of his pre-war generation. It seems to require a certain innocence or even naïveté, as well as a kind of inner atmosphere of austerity and frugality." And I am struck by that not least because of the eloquent conviction with which it illuminates a way of being that has passed.

What else are memoirs for? The guiding force behind such works as Philip Roth's Patrimony or Blake Morrison's When Did You Last See Your Father ("My father, methinks I see my father", also not by Ricky Gervais) is a similar compulsion to mark the demise of a certain sort of man. There is nothing sentimental about this. No hankering after the past out of mere temperamental disinclination for the present. Nor is it to be confused with poor Rita's outburst against our trashy times in Coronation Street last week. "I'd like to propose a toast to the end of an era," she declaimed tearfully into her valedictory champagne, having been found guilty of clipping a lying little tealeaf round the ear, "an era of honesty and decency."

A sentiment with which the entire nation will concur, for we all know there is small savour left in life when you cannot clip a tealeaf with impunity. But Rita's lament is open to the charge of civic nostalgia, and there will be plenty of historians of delinquency lining up to tell her it was ever thus.

Which is why it's important we do not mourn the wreckage of British Intelligence in Rita's terms. Not because now is frightening and uncouth do we need to own the language of another time, but because we are bound to the past by a delicate tracery of obligation and loss. We cannot apprehend who we are now if we cultivate ignorance of how we were then, or deafen ourselves defiantly to what once was music to our ears.

That "thrillability" which James Lasdun associates with his father is no less ours because we've lost it. We are what we once had the potential to be, and if we don't know that we are no one.