This has always been true of museum collections - but, till now, their meaning has stayed more or less the same. This has led to the illusion that the value of museums lies in their collections - not in the meaning of their collections. Things get stuck, thoughts flow.

The single most important thing that museums have to realise today is that the meaning of their collections is changing - not marginally, but fundamentally.

Museums began as bi-products of the Enlightenment. It made sense to put coins in chronological rows. Whole dynasties of Emperors were discovered by this simple process. Charles Darwin collected every type of barnacle and worked out the theory of Evolution. But scientific research has long gone beyond what's materially collectable - even what's visible. Many museums blindly act as if it hadn't. The British Museum's coin department is now collecting credit cards. What does this museum - which claims to be one of the world's greatest repositories of human culture - think it's doing?

Most museums, however, have virtually given up collecting. Faced with the plethora of contemporary production, they don't know where to begin. That's because they've given up thinking what they're collections could mean.

The social meaning of museums has changed. They're no longer primarily institutions collecting evidence for research - though they still have this function in part - a little part. As far as the public is concerned, their primary and urgent function is to collect our meaningful past.

There is an urgency about this because younger generations are losing their link with the past. It is one of the jobs of museums to maintain that link.

One of the most significant developments in recent history has been Communism. The vital evidence that can bring its history to life - with all its hopes and terrors - is, as we digest, being lost. But what museum could take on such task -one in Russia? Russia is too partial - and doesn't at present have the political appetite for such a task. There's one obvious candidate. The British Museum claims to be a museum of world culture - and Communism was cooked up in its own Reading Room! Communism is part of that museums' history. Like Nazism, it was a late product of the Enlightenment.

The British Museum argues that by continuing to collect in the categories it does - coins, ceramics and works on paper - it will amass the evidence of communism along with everything else. Who's it kidding? The history of the 20th century is on film. But the British Museum doesn't collect film - why not? - because it wasn't invented in the Enlightenment.

All categories of collecting - including the totally anachronistic division between archives and museums - are irrelevant to modern society. Meaning is the only category for collecting - and the significance of their collections will be only thing that will ensure museums have any meaning for future generations.

What's all this to do with the theme of this conference? Everything - because movability is everything.

As the nurse used to put it politely - have you had a motion? Museums haven't had a motion for years.

If you had to absorb everything you've just eaten, you'd soon feel constipated. That's exactly what museums feel today. But they're not just constipated with old things - they're constipated with old thoughts.

So here's my little pill.

I hasten to say it's not a restructure - we all tried that in the eighties and nineties and learnt it made no difference. People were given different job titles but always found a way to wriggle round and go on doing what they'd always done.

What's needed is not a restructure, but a change in attitude - above all towards lending - because lending is a museum on the move. Lending's the wrong word for a start - because museums don't own their collections - the public does - so we can really only talk about public borrowing, not museum lending. We can only talk about the right to borrow - not the right to lend, or not to lend.

In my view, museums do not have the right to say no to a request to put on safe public display any item that is currently in storage. In the modern age of museums, public need must take precedence over the needs of the scholar, who can anyway travel to see an object on public display wherever it is.

Safety of access is of course important because we do not want to lose or damage the relics we treasure. But it's no good preserving something if no-one can ever see it. Which is why the conservator's job - the museum conservator that is, not the private conservator - they're different but you'd hardly know it - the museum conservator's job is not just to make the collections safe - but to make them safely accessible.