Jeremy Bentham, the great utilitarian, was a man who practised what he preached. He owned a pair of houses in York Street, Westminster, and sensibly lived in one while renting out the other. The other happened to be the house where Milton once lived. Bentham let it to his colleague James Mill, whose son John Stuart Mill passed the early years of his life there, studying Greek and Latin under his father's eager tutelage - to the point where he nearly lost his mind. When the elder Mill quitted the house complaining of its darkness and damp, it was leased by the great essayist William Hazlitt, who lived there from 1812 to 1820, in which year Bentham evicted him for non-payment of rent.
Bentham was not in the slightest bit interested in the literary associations of his next-door property. At various times, he contemplated demolishing it to enlarge his garden. In the end, Westminster City Council, as utilitarian in its practices as Bentham himself, knocked down both the Milton-Mill-Hazlitt house and Bentham's own. It is natural to think that the 19th century was not squeamish about destroying iconic places in the way that we are now, and that Bentham's attitude was typical of its time. But matters were not so simple. Hazlitt was acutely aware of the risk of historical Luddism posed by Bentham towards his house - which he honoured as Milton's house, unchanged since Milton's time - and he was appalled by it. The opposing views of Bentham and Hazlitt have become the staple of the debate about conservation, a debate that, in their day, did not take the form, or have the urgency, that it now does, only because the rate of change was then slower, and far more of the past was present.
The Bentham view was long the orthodoxy, and it scarcely seemed to need arguing. It is a mistake, it says, to hang on to the past merely because it is past. Things - buildings, paintings, old furniture - have their lifespans as humans do and, when they get old and broken, dirty and inconvenient, decrepit and even dangerous, we should let them go. The past becomes a burden if we have too much piety towards it. Salvaging some things merely because they have existed for longer than other things is an inhibition to progress and a barrier to new ideas and fresh ways. The older things get, the more that current resources are needed to prop them up, repair them and keep them safe. The past might live in the present, in the sense that old things might still be used and enjoyed; but as soon as they become mummies or museum items, they are merely baggage.
This view incorporates several strands. It attacks the physical and financial burden, generally an increasing one, of keeping old things in existence. It attacks the psychological burden of being wedded to the past and thereby inhibited from innovating. It attacks historical pietism as a disguised form of timidity, always a major element in conservative attitudes. And it makes the good point that things, like people, have natural lifespans; and that, unless we move forward, we sink - look at China from the Song dynasty (which began in 960 AD) to the Qing dynasty (which ended in 1911 AD) as a prime example of almost complete entrapment and stultification in tradition (although not in ceramics or prose literature, thank heaven).
Holders of the opposing view say that, without respect for the past and understanding of it, we are blind and deaf to the present. Maintaining access to the past in the form of traditions, buildings, works of art and places of special association gives us a far richer and deeper insight into our route hither through time - and, therefore, into ourselves now and our possibilities for the future - than if we had lost all palpable trace of it. For example, a written or even photographic record of the remains of the Rose Theatre at Bankside - built in the early 1590s (before the Globe), and the scene of Marlowe's triumphs and Shakespeare's beginnings - could not compare to the impact, both emotional and educational, of seeing that tiny space in its polygonal footings, with its sloping clay pit-floor and the foundations of the stage, and knowing that this was the very place, and these the very things, that saw the birth of all that wealth.
And even when the meanings of our present culture are not so vividly linked to the past in this way - even when the past is remoter, more silent, seemingly unconnected with the present, as with Stonehenge ("that huge, dumb heap, that stands on the blasted heath, and looks like a group of giants, bewildered, not knowing what to do, encumbering the earth, and turned to stone, while in the act of warring on Heaven") - we would be committing sacrilege against our present selves if we bulldozed it to make way for a council estate. The very suggestion sends a chill; and it repays to investigate why.
The march of the 20th century, a blitzed, bombed and murderous epoch in which many of the cities of Europe - London, Berlin, Dresden, Warsaw - were subjected to terrible physical destruction, and in which not only buildings but tens of thousands of artworks and archives were lost, has seen a corresponding growth of official historical consciousness, as if in compensation. It has got to such a point that it now seems to critics as if far too many things, in apparently indiscriminate profusion, are listed, protected and preserved. An egregious example often cited is the rebuilding of the old centre of Warsaw - "dov'era, com'era", as was said of the collapsed campanile of Venice ("where it was, as it was") - as an exact replica of its former self. Walking through it makes one uncomfortable; it is ersatz, and feels like a mistaken gesture, a refusal to face facts and move on. The anxiety to preserve and even to recreate "heritage" has, critics say, gone too far, inviting all the strictures of the Benthamite view.
But Warsaw is actually an unusual case, and its purpose was more a matter of psychology than historicism. Its gutted heart was a deep and savage wound, and rebuilding it was medicinal, restoring landmarks as homecoming beacons after a terrible disorientation. Few other places followed suit. In London, as the famous Surveys of London showed, a quiet sigh of relief went up when the City, the East End and the areas of south London close to the Thames were opened for renovation by the Luftwaffe. There had been precious little of value there anyway. The City itself is an architectural palimpsest, constantly being rebuilt, an expensive throw-away region very short on real treasures - except those the mind sees, walking streets that are yards deep in historical meaning. New office blocks in the City have a projected life of a few decades only and, with rare exceptions, their design is as utilitarian as Bentham could wish, at most involving a few cosmetic gestures. The opposite of conservation is built-in ephemerality; the City is not for conserving - is not for history, but economics - and, as in its investment practices, it is interested only in the short term.
It happens that conservation is no longer purely a matter of sentiment or intellectual commitment. Heritage is a major source of tourist revenue, and if Bentham had realised that he could charge a penny a time for punters to troop through the house where Milton dictated Foreign Office missives in Latin, and Hazlitt scribbled notes for his essays on the wainscoting, the best utilitarian principles would have galvanised him into sprucing the place up and conserving it tenderly. One of the chief safeguards of the past is that it has become a leisure resource. But this applies only to obvious things, such as cathedrals and castles and places of literary association - for example, the houses of Dr Johnson and the Brontes. There is much of interest and value that lies off the tourist track: stone-age hill forts, barrows and mounds, Roman pavements, the multiple strata of archaeology underpacking London; and more recent items such as the Lloyds building, Battersea power station, and Antony Gormley's Angel of the North. If the debate about conservation has a bite, it relates to these things.
Thinking about a choice between Stonehenge and a council estate focuses the mind on one clear point: that it is better to err on the side of preserving because, if one makes a mistake in so doing, it is remediable, whereas post facto regret is no remedy. Current policy on historical conservation in Britain thus makes the right error. And it is not even clear that it is an error: after all, 90 per cent of planning applications in respect of listed buildings are granted and, for all the criticism it receives, English Heritage appears to be conscious, in its practice as in its stated policy, that the past competes with the present and future, and that they deserve equal if not more consideration.
A healthy attitude towards conservation combines a sense of the strength of Hazlitt's side of the argument with a robust scepticism about why so many tithe barns and Georgian terraces have to be fenced off from progress. If time and leisure permitted, every candidate for conservation or restoration would be examined on its merits; and, if kept, it would be properly kept, at the same time being integrated into the life of the present as far as is practicable. But time and leisure do not permit, which is why one needs principles and policies. Current policies - erring properly on the side of caution - are good. The principles are that things good of their kind are worth keeping for their own sake, and that there are also things worth keeping for the sake of understanding the past and therefore the present. The principles justify the policies.