EDSAC I, nearly complete, W. Renwick.

Several centuries ago, a short, ugly Frenchman, Rene Descartes, proclaimed that the human body and the human mind live in two different worlds - that there exists in humankind a "dualism". The human body, he declared, is just a machine with joints and muscles instead of cogs and pistons, while the human mind is something non-physical, a life-force in a world of its own.

His approach was the perfect solution to a significant problem at the time. Science was rising out of the Renaissance and was keen to get its hands on the human being, but Religion, which had traditionally held the rights to all truths in that area, was not ready to give it up. Then Descartes swung his axe and split humans down the middle. The scientists were left with the machinery, the clerics with the divine - for centuries it was a great arrangement, but it couldn't last forever. Eventually, Science began applying its science-sense to the mind too, and the conclusion had to be that Descartes was wrong all along: "how could something non-physical exist", the scientists tittered, "let alone hold sway over something physical. Don't bother handing the ‘mind' over, Religion - you've got nothing."

Science's bravado was, in part, fuelled by the development of a new type of machine - a machine that, had it existed in Descartes' time, might have ruined the framework of his argument, because this machine was astonishingly clever and built not of heavy cogs and pistons, but microscopic electronics, just like the brain. The computer - a machine built to compute, to solve problems. And it had a special quality - it was, theoretically speaking, future-proof. If you got the hardware right, you wouldn't need to change it again: all you'd ever need was the latest software.

Of course, we now know that those first, mid-Twentieth century computers were far from future-proof - the size of a barn and barely able to remember their own names - but suddenly, with a machine like this in existence, it wasn't so hard to imagine that we were simply very impressive, organic machines, and that Descartes' "mind" had been a phantasm: he'd heard the wind rattling the windows and jumped to the conclusion that we were all haunted.

But Descartes' dualism didn't end there. The scientists had forgotten something - many of their fellow scholars still believed in ghosts. The thought that humanity might only be a matter of matter - of brain tissue - was too much to bear for the majority of social scientists and humanists. They thought that they saw so much more. The only option available to them was to declare that the experiments of Science can tell you only so much - that there is something else to believe in, something beyond the observable. Belligerent and proud, they grabbed hold of Religion's "mind" and sheltered it in their studies. Their number included psychologists, anthropologists, economists, political scientists, cultural theorists and sociologists - in short, all the people that we collectively hire to investigate humanity.

So it is that Descartes' dualism is alive and well, manifest in the way that we study humankind today. The natural scientists, the brainiacs, maintain that humanity is just a machine, a matter of matter, and get on with their work with that in mind. The social scientists and humanists, the mentalists, are convinced that something "extra" lies within, and continue their work on that basis. The two bands don't talk to each other much, and when they do it's often not nice. Natural scientists are labelled "reductionists" - people who consider complex systems as nothing more than the sum of their simple parts. Social scientists and humanists are accused of being "antipositivists" - people who reject scientific explanation in favour of untested theory. What neither side seem to appreciate is that, for the recipients of the abuse, these terms are often not insults but accurate depictions of their positions. People differ on how they find truth, and that truth is likely to continue.

How do I find truth?

We forgot about the computer. While everyone's been arguing about whether our brain is like a computer or not, computers have changed. Instead of standing mute in the corner of a room, beeping while they carry out inane routines, they're all talking to each other down telephone lines, planning our days and entertaining us. Across the net and via the web, every connected computer is swapping files and software with every other. They keep themselves up to date with updates, whether they're the latest, shiny offering from Apple or a rattling box of plastic made in some developing world sweathouse with a modem stuck in its rear. They don't have to have a huge memory, because the weird thing about the internet is that the information doesn't appear to exist anywhere real. It must be housed on hard-drives somewhere, but because everything is shared out, because the memories of the millions of individual computers are now inter-connected, it doesn't exist anywhere, but everywhere, in a space that doesn't relate to any volume in the physical world. It's a non-physical world - cyberspace. There's so much more to machines these days than cogs and pistons. How would Descartes have been inspired by all this?

Here's my stab at a modern Cartesian model:

• machine = body - just as before;

• computer (a very particular machine) = brain (a very particular part of the body) - every individual machine can operate alone, and has its own memory and operating system, and it's own unique loading of files and software;

• network protocol = channels of communication between these special machines, i.e. language, the stuff that connects all our brains together and let's them swap "files";

• contents of the world wide web = culture - the files and software themselves, the information and applications that we all have access to;

• cyberspace = the realm in which this cultural information resides. There isn't an agreed term for this place, in fact most people don't even recognise it as a place at all. A Russian geochemist called Vernadsky once called it the "noosphere", the "world of human thought", so let's go with that.

Now we have network computers it doesn't look like Descartes was so far out after all. Now, we can see two worlds at play. Not the worlds of "body" and "mind", but the worlds of "biology" and "culture". Our physical selves, our bodies and brains (the machinery), are born of, and operate in the biosphere - the global sum of all biological Life. All those aches and pains, those teenage spots, those inconvenient bodily functions, those wrinkles and liver spots - they're all side-effects of our biological existence. For every other creature on the planet (probably), biological existence is all there is. But we humans have, quite accidentally, accessed another world, a world of our own - the place of cultural Life. Mother Nature (who runs the biosphere) lost us to this place, the moment she made us smart enough to swap ideas, the moment she gave us the power to do culture. When our distant ancestors, (way before cave-people), first dipped a toe in this place, it was vacant. But the inheritable thoughts of those ape-humans seeded a new kind of Life in that non-physical other-sphere - cultural Life, where ideas were the life forms, subject to a new kind of evolution - cultural evolution.

This evolution did what evolution does, it built upon those simple beginnings to create, over time, an enormous tree of new Life, getting ever more complex and differentiated. Now, tens of thousands of proto-human and actual-human memories later, this noosphere is vast, in fact comparable, we may immodestly suggest, to its parent biosphere.

Those songs that you can't get out of your head, those childhood nightmares, those quiz answers that flirt with the tip of your tongue, those awkward remarks that you wished you'd never made - they're all side-effects of your cultural existence - your engagement with this other world. The solution to Descartes' "mind" conundrum perhaps lies in appreciating this different kind of dualism within each of us. Brains are biological. Our minds are cultural - our avatars in the noosphere, existent, but only about as physical as a Google search.

Image Copyright Computer Laboratory, University of Cambridge. Reproduced by permission.

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