LONDON: It always sounds exhilarating, how the internet is going to liberate us from the mundane shackles of a single existence. While the major world religions promise sequential lives (one now, a second instalment after death), cyberspace offers parallel pathways through this vale of tears. By 2011, apparently, the great majority of us will have at least one avatar or digital representation that busies itself with an online life that is the same – although, crucially, not identical – to the one that gets played out more prosaically in real time and space.

Before you get too carried away with the giddying possibilities of a Second Life, take a look at The Golden Compass, the new film of Philip Pullman’s fantasy novel Northern Lights. In the book the principle of each character having a “daemon”, a kind of externalised identity in animal form, worked brilliantly. But watch the whole bristling, chirping world of feathery, furry doubles come to life on screen, and you see that having an alter ego is probably more trouble than its worth.

For a start, how to choose the form your daemon would take? In cyberspace you can opt for an avatar that is younger and sexier than you are, secure in the knowledge you will never be asked to present your real-world self. But Pullman’s daemons walk alongside you every step you take. Choosing to follow the example of dashing Lord Asriel by having a snow leopard as your familiar is all very well, but it takes a lot to live up to. Fine on a day when you’re feeling chipper, but who wants to be seen alongside a magnificent feline beast when you haven’t had time to wash your hair. Far better to pitch your aspirations lower – a tabby with a touch of mange – and give everyone a pleasant surprise when you follow your familiar into the room.

Then there’s the fuzzy metaphysics of Pullman’s world, which suggests the form your daemon takes says a lot about you. Asriel, by being represented as a snow leopard, is revealed as noble, graceful and, presumably, effective in sub-zero temperatures. The elegant Mrs Coulter, meanwhile, is given away as a baddie by the fact that her daemon is a grumpy monkey. Dating would become delightfully easy in a world of Pullman-esque plurality. No matter how kind and attentive the man sitting opposite you in the restaurant, the fact that he had an ugly, dribbling toad sitting on his shoulder would disincline you from a second meeting. Briefings with the boss would go so much easier if, despite her frosty manner, she was accompanied everywhere by a spaniel that insisted on rolling over and having its stomach tickled.

I have witnessed only one instance where having a daemon worked, and it occurred in the real world. Anyone who had to endure the former British government minister David Blunkett, who is blind, on the publicity trail for The Blunkett Tapes would have been entranced by Sadie, the black labrador guide dog that accompanies him everywhere. While other daemons might roll their eyes when forced to listen to dull stories for the 10th time, Sadie always managed to look interested. On the rare occasions when it got too much, she went to sleep at Blunkett’s feet, snapping to daemon duty again when a tepid applause spattered round the hall.

Even so, Sadie doesn’t do housework, filing or answering the phone. In which case, one comes back to the essential philosophical question of what a double is actually for. Even those avatars racing around the internet apparently need the services of something called an “identity manager” to keep them up to date and on track. They don’t – just as daemons don’t – have a useful, productive existence independent of the person who created them. Until that moment comes, they remain yet another smart accessory that is more trouble than it is actually worth.—Dawn/ The Guardian News Serivce