There are moments when the reader wonders where Johnson is going: he can become so involved in a particular aspect of his argument (the development of the internet and of computer games, for example) that the broader picture - the nature of emergent systems, and their uses in, or relevance to, our lives - can seem a little distant. The book as a whole would have benefited if the theory and science of the early chapters had featured more strongly in the latter half. But Johnson writes so well, in such an enjoyable, enthusiastic style, that the book never becomes hard work.

'Emergence' is a good book that will appeal to anyone (and I mean anyone - this isn't a book just geeks or boffins) who enjoys looking at the world around them in challenging new ways. And it is a book with a long life - you are sure to return to it, flicking through the index to find Johnson's lucid take on one thing or another.

By contrast the second half is more speculative, in particular whether the world wide web is emerging and thus whther it will - like SkyNet in the Terminator movies - become sentient. It might interest many readers, but personally I would have preferred the pages devoted to a deeper - slightly more scientific - view of how the simple rules (e.g. get close, but not too close, to your neighbour) can lead to complex organised behaviour (e.g. birds flocking without any "leader" in the sense of one that the others follow).

Overall a good book, and one worth buying and reading to the end, but one that Dawkins could have done better.

In an emergent system, complexity is organised from bottom to top. There is no hierarchy or rules imposed onto a system from a minority, but a set of basic rules that will govern local interactions that in turn will create higher organisation and the emergence of a complex and sophisticated behaviour from the whole.

Johnson starts by exposing the Myth of The Ant Queen allegedly ruling from the centre of her kingdom and bossing around billions of workers ants. Ants in fact obey a set of simple and basic rules that will determine local behaviours which, when combined, will produce an orderly and working society.

It is then an easy step to move from an ant colony to human society and in particular the way our towns are organised. Johnson underlines the work of Jane Jacobs on the importance of street walks. Street walks are where the "human ants" interact and decide the local organisation of their environment. The results of these local interactions will decide the overall appearance of the area, the nature of the people living there, the shops and so on. For someone who has been living for some time in the same place, I suppose it is easy to see how things change, but not always why they have changed.

This theory could suggest that everything is ever changing. However, and at least on the Old Continent, patterns that have resisted the passage of time are still observable. For example, the Jewellers of Ponte Vecchio in Firenze, the Parisian trading centre of Les Halles, the Fashion designers of Carnaby Streets in London. These patterns are an important part of our learning ability and, interestingly, can be encoded into computational programs that can be used to improve the Internet (or to produce games such as Sim City).

Alexa was one of the first programmes able to establish connections between websites of similar interests. The connection was not based on the programme investigating and deciding which sites were of similar nature but on the habits of the net user, surfing from one site to another, Alexa was only trying to identify a navigation pattern. The results could sometimes be surprising. A variant of Alexa is now embedded in your browser (mine is turned off; where I surf is no one else business).

But what was missing was a feedback function. A function that would regulate the system and improves it. Here Johnson moves into a territory of great interest for the Blue Ear community. Taking the example of SlashDot and its thousands of users and contributors, Johnson explains how an open editorial feedback was set up in order to filter the spam and the cranks from the good quality contributions. The readers would mark each contribution from -1 to 5, and it would be possible to select the contributions accordingly, reducing the signal/noise level.

Emergent behaviour can be recreated "in vitro", and computer software can become emergent when put under the stress of a selection process. There is quite a lot of similarity between the Theory of Emergence and the Theory of Evolution whether we consider Darwin, Gould or Hawkins. When Hawkins would probably see the selection of the genes as the bases of its theory, Gould would probably see the selection of patterns of genes. It is a possible way of reconciliation for both theories.

Emergence raises the question of control. Who controls what exactly in an emergent world? When the rules are not set from top to bottom but are decided locally, and when these rules ultimately determine the choice of those who govern us, this is very unsettling. Seen from this angle, globalisation as a means for oppression in the hands of a few becomes its antithesis: an oppressive tool shaped and controlled by those who claim that they are oppressed, an oppressive tool in the hands of all. Strangely, it is something I have always suspected.

It was overall a very interesting reading. It is clear enough even for those who know very little about computer science or ants. The only downfall is a system of notes that is far from emergent.