It is the fate of teachers to be educated by their students. At Brown this happens often, and it continues after students become alumni. Having left the University with a concentration in semiotics, Steven Johnson '90 went on to graduate school at Columbia but stopped short of the doctoral degree to help found and edit feedmag.com, an online magazine devoted to technology and culture. Feed, a great success during the dot-com era, folded last June, when, despite its relatively minuscule budget, the Web site's money ran out.

Fortunately, Johnson has also been using the more conventional medium of books to communicate his ideas, and publishers are still willing to fund them. I remember Johnson at Brown as an exceptional student who flaunted an ornate prose style but who thought with originality and vigor. I am happy to report that in Emergence: The Connected Lives of Ants, Brains, Cities, and Software, the prose is now as clear and user-friendly as one could wish, and the thought continues to be vigorous and original.

In his first book, the 1999 Interface Culture: How New Technology Transforms the Way We Create and Communicate, Johnson presented a McLuhanesque argument about the way media shape human perception of the world. He illustrated this by discussing the art and literature of past ages as shapers of the pre-digital worldview, and by claiming that the digital interface was reshaping human perception in our own world. Emergence is about the way higher-level systems emerge from the behavior of individuals at a lower level, without direct leadership by "pacemakers" from above. Individual ants, for instance, react to a very limited range of stimuli, but their collective behavior creates and sustains a self-regulating social entity, the ant colony.

Similarly, Johnson argues, the more complicated individual choices of people living and working in cities lead to self-regulation of the social group, creating neighborhoods that are safe to live in and other groupings that generate commerce, art, and ideas - all of this without the benefit of "planners," who often make things worse when they intervene in the self-regulating patterns of urban life. In his discussion of cities, Johnson gets powerful support from two sources, Jane Jacobs's The Death and Life of the Great American Cities and a late-1950s Rockefeller Foundation report by mathematician Warren Weaver that introduced the notion of "organized complexity" that Jacobs adapted to describe city life.

But ants and cities are only two of the sorts of organized complexity Johnson mentions in his subtitle. The others are brains and software. In his previous book Johnson emphasized the way human minds function through the recognition of patterns and the visual organization of what they perceive. This, for example, is why the popularity of computers really took off when the easy-to-use graphical interface of the Mac and its Windows derivatives replaced the mysterious command line of the early mainframes and such early PC-based operating systems as DOS. The brain, as Johnson points out, can "perform amazing feats of pattern recognition, feats that continue to confound digital computers" because the brain is a "massively parallel system." The brain, in other words, is slow at doing serial calculations - the sort of things computers manage with blinding speed - but very good at making comparisons and recognizing patterns, the things that are crucial to our visual arts and music.

Software plays the crucial role of connecting the serial power of digital calculation to the visual and verbal patterns at which humans excel. Thus, we can see our "desktop" and organize our documents in "folders." And thus we can play games that insert us into narrative structures and visual scenes.

But the new media are also interconnective and interactive. That is, the Web connects us and allows us to interact with one another and with the corporate entities that compete for our attention. Johnson gives a fascinating account of ways certain Web sites have used "filters" to rank documents in an order of interest, based on visitors' behavior at the site: the way, for example, Amazon.com will recommend books based on a buyer's previous purchases.

Johnson sees filtering as a solution to the problems of information overload, as a way of bringing order to the chaos of infinite choice. As examples of digital culture regulating itself through feedback mechanisms, he offers the quality filtering at Slashdot.org (where viewers get to rank what they see) and the ability of viewers on eBay to check the history of past deals, and he notes the enormous appeal of such emerging systems - eBay alone has attracted more than 30 million users. In such developments Johnson perceives the possibility of a utopia of emergence, in which "the tools of feedback, neighbor interaction, and pattern recognition" are allowed to operate to build a better world - but he leaves open the question of whether we will actually move in this direction.

So, I can imagine you thinking, What's the bottom line here? Is this a book I need to read (or know enough about to fake it), or can I safely ignore it? Well, "emergence" is a concept that is now all around us - just punch the word into Google and you'll see - and you will find no better introduction to it than this lively, witty, and splendidly lucid book. It is a pleasure to watch Johnson range elegantly across the history of human culture and the intricacies of modern science and technology. He is a charming guide, and his book will give you food for thought and for conversation. Johnson's Web magazine was not called Feed for nothing.