John L. Casti is at Complexica, Santa Fe, New Mexico 87505, USA, and the Institute for Monetary Economics, Vienna, Austria.

Alan Turing: Life and Legacy of a Great Thinker
edited by Christof Teuscher Springer: 2004. 542 pp. £46, $69.95, 59.95

In 1999, Time magazine made Albert Einstein its 'man of the century' for the work that changed our view of time and space. It's difficult to argue too strenuously with this choice. But when it comes to scientists who have affected daily life, a far better choice would be Alan Turing, the British mathematician turned computer scientist whose invention in 1936 of what is now called the Turing machine was the theoretical backbone for every one of the zillions of computers in use today. Not
only did Turing provide the key theoretical element for computing machines, he helped to build one of the first electronic computers, in Manchester, UK, shortly after the Second World War.

This book is the outgrowth of a workshop held in Lausanne, Switzerland, in June 2002 to honour the ninetieth anniversary of Turing's birth on 23
June 1912. Turing's work was so broad and deep that another gathering this year, to mark the fiftieth anniversary of his death, would not be
out of place.

It is difficult to find the superlatives to describe the wonderful job the contributors to this book have done. Every chapter is written in an expository fashion, demanding very little in the way of background knowledge from any scientifically minded reader. The range of topics is
also impressive, with sections on Turing's life and thoughts, the theory of computation and the Turing machine, artificial intelligence and the Turing test, the wartime Enigma code-breaking work and, finally, forgotten ideas.

Each section contains between two and seven chapters that explore themes ranging from what Turing might have thought about today's work in
'hypercomputation' — a field that explores information processing beyond the abilities of Turing machines — to his ideas on thinking machines and robots. The book's contributors are as sterling a collection of computer scientists, philosophers, engineers and historians as one could ever wish for, including logician Martin Davis, philosophers Daniel Dennett and Jack Copeland, technologist Ray Kurzweil and historian Andrew Hodges.

In her extremely entertaining chapter "Alan's Apple: Hacking the Turing Test", the Italian writer and theatre director Valeria Patera creates a theatrical setting in which eminent figures in artificial intelligence meet in a virtual plane to consider Turing's ideas on thinking machines.
A staging of this might be more interesting, intellectually at least, than the rather dull play "Breaking the Code" that ran so successfully
in London and New York some years back.

Two of the more provocative contributions come from Davis, who argues against the ideas put forth by a number of researchers for transcending
the Turing barrier in computation, and from Kurzweil, who explains in detail his well-known arguments for why technological progress will
occur at such a pace that machine intelligence will surpass the human variety within a few decades.

On the principle that no book is perfect, I have to admit to one small quibble. Given Turing's great interest in biological processes, especially near the end of his life, and his pioneering work on what we
now call mathematical biology, I was disappointed to see only one of the 20 chapters devoted to that aspect of his work. Of course, no book can
do everything, and this short-changing of biology in favour of computing is more of an opportunity than a problem. Nevertheless, a couple more chapters on morphogenesis, artificial life and so on would have really made this book the definitive volume on Turing's work and its implications.

I unreservedly recommend this book to anyone even slightly interested in the continuing role of Turing's work in the development of computer
science in particular, and ideas in general. Conference proceedings rarely make for good reading and are generally strange beasts to review. This volume is the exception that proves that rule.

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