The Science of Discworld Revised Edition

about the architecture of the brain. The viewpoint is that this determines what brains can do, and then the various things that we associate with minds – the difficult problems of free will, consciousness and intelligence – come out of neurophysiology. That’s one approach. The other common one is to view the problem through the eyes of a social scientist or an anthropologist. From this viewpoint the mind’s capabilities are pretty much taken as ‘given’, and the main questions are how human culture builds on those capabilities to create minds able to think original thoughts, feel emotions, have concepts like love and beauty, and so on. It may seem that between them these two approaches pretty much cover the territory. Link them, and you have a complete answer to the question of mind.
    However, neurophysiology and culture aren’t independent: they are ‘complicit’. By this we mean that they have evolved together, each changing the other repeatedly, and their mutual coevolution built on the unpredictable results of that ongoing interaction. The view of culture building on, and changing, brains is incomplete, because brains also build on, and change, culture. The concept of complicity captures this recursive, mutual influence.
    We call the brain’s internal capabilities ‘intelligence’. It is convenient to give a similar name to all of the external influences, cultural or otherwise, that affect the evolution of the brain – and with it, the mind. We shall call these influences
extelligence
, a term that H EX has picked up thanks to once-and-future computing. Mind is not just intelligence
plus
extelligence – its inside and outside, so to speak. Instead, mind is a feedback loop in which intelligence influences extelligence, extelligence influences intelligence, and the combination transcends the capabilities of both.
    Intelligence is the ability of the brain to process information. But intelligence is only part of what is needed to make a mind. And even intelligence is unlikely to evolve in isolation.
    Culture is basically a collection of interacting minds. Without individual minds you can’t have a culture. The converse is perhaps less obvious, but equally true: without a shared culture, the human mind cannot evolve. The reason is that there is nothing in the environment of the evolving mind that can drive it towards self-complication – becoming more sophisticated – unless that brain has something else fairly sophisticated to interact with. And the main sophisticated thing around to interact with is minds of other people. So the evolution of intelligence and that of extelligence are inextricably linked, and complicity between them is inevitable.
    In the world around us are things that we, or other human beings, have created – things which play a similar role to intelligence but sit outside us. They are things like libraries, books, and the Internet – which from the viewpoint of extelligence would be better named the ‘Extranet’. The Discworld concept of ‘L-space’ – library-space – is similar:
it’s all one thing
. These influences, sources not just of information but of meaning, are ‘cultural capital’. They are things that people put out into the culture, which can then sit there, or even reproduce, or interact in a way that individuals can’t control.
    The old artificial intelligence question: ‘Can we create an intelligent machine?’ viewed the machine as a once-off object in its own right. The problem, people assumed, was to get the machine’s architecture right, and then program intelligent behaviour into it. But that’s probably the wrong approach. Of course, it is certainly
conceivable
that the collective extelligence of all the human beings interacting with that machine could put a mind into it – and in particular endow it with intelligence. But it seems much more likely that, unless you had a whole community of machines interacting with each other and evolving, providing the requisite extelligence too, then you wouldn’t be actually able to structure the Ant Country of the neural connections of the machine in a way that could generate a mind. So the story of the mind is one of complicity and emergence. Indeed, mind is one of the great examples of complicity.
    The internal story of the development of the mind can be summed up as a series of steps in which the key ‘player’ is the nerve cell. A nerve cell is an extended object that can send signals from one