Idea back in the dock

What are the "big" questions facing modern science? John Casti thinks he knows. Who can fail to be interested in an authoritative overview of such scientific debates as the origin of life or whether computers will be able to think?

These are two of the six topics that Casti explores in Paradigms Regained . The other four topics are equally compelling -genetic imperialism and Darwinian evolution, the origin of the apparently unique ability of humans to learn languages, the search for extraterrestrial intelligence and the mysteries of quantum mechanics. One might argue that understanding consciousness and/or quantum gravity should also be on his list, but it is certainly not a bad start.

The problem is that Casti has already written such a book. The title of this book echoes the title of its highly praised and successful predecessor, Paradigms Lost , published in 1989. There are therefore two questions to be answered. First, has sufficient scientific progress been made in ten years for a sequel? Second, is the sequel intelligible to someone (like myself) who has not read his first book?

To make the scientific debate entertaining and readable, Casti structured Paradigms Lost in the form of a trial: he summarised the evidence for prosecution and defence before casting his vote as a member of the jury. His new book attempts to retain this successful formula and uses the metaphor of a legal appeal, with fresh evidence and possibly a different judgment.

The difficulty with this approach is that Casti has to introduce each "case" with a very rapid summary of the arguments presented in his previous book. Since these are complex issues, I cannot help feeling that those who have not read the first book will find this pretty tough going. Two examples will make the point. Although not an expert on genetics, I have read many popular accounts and like to feel that I have some understanding of the basic mechanisms involved. Nonetheless, I found Casti's summary of the genetic code irritatingly obscure in its brevity. Similarly, in any discussion of the nature of quantum reality, some understanding of the famous Bell inequalities is mandatory. Again, although in this instance I do have first-hand knowledge of the subject, I found Casti's discussion particularly unhelpful.

Having said this, there is clearly much in the book that will delight and intrigue. The opening chapter reprises the delicious hoax played by physicist Alan Sokal on a prominent postmodern journal. Casti also takes up a number of other interesting issues including what he calls the "mediazation" of science -which he illustrates by reference to the phenomenal success of Stephen Hawking's A Brief History of Time and to the cold-fusion fiasco. The puzzle of "junk DNA", life from outer space, Nasa's Martian meteorite and the US Supreme Court's ruling on evolution feature in the next chapter on the origin of life on Earth.

There are surveys of the sexual fidelity of mountain and prairie voles and of the intelligence of 240 pairs of Swedish octogenarian identical twins; of the eating habits of black rats in Israel and macaque monkeys in Japan; of the cooperative behaviour of the Arabian babbler and of the uncooperative behaviour of the bowerbird.

There is a similar store of arcane facts in the chapter on language. The mechanisms for learning regular and irregular verbs are apparently "neurologically distinct", while the rongorongo inscriptions on Easter Island and the tree runes on an English Dark Age stone cross remain undeciphered.

One of the inspirations for reopening the debate on artificial intelligence is world chess champion Garry Kasparov's defeat by IBM's Deep Blue computer: Kasparov is quoted as sensing a kind of "alien intelligence". Another is Casti's evident desire to set the record straight after the success of Roger Penrose's bestselling "anti-AI" book The Emperor's New Mind . He recounts the many arguments that have been used to demolish Penrose's appeal to Godel's theorem. In the search for extraterrestrial intelligence, the major new fact is the discovery of planetary systems around other stars. Apart from this development, I have to confess that I find the whole debate about how to assign values to a set of manifestly unknown quantities about as convincing as Steven Spielberg's expert in extraterrestrial communication in Close Encounters of the Third Kind .

Where there has been a surprising amount of real progress in the past ten years is in the realm of quantum mechanics. Casti begins by recounting the surprises of "interaction-free" measurements leading to the quantum zeno paradox -a watched "quantum kettle" never boils! He ends the book with a survey of recent experiments on quantum teleportation and how Richard Feynman's speculation about quantum computers could become a reality. Sadly there is space for these fascinating topics to be given only the most cursory treatment.

So what is the verdict? Although Casti's sequel may be hard-going for someone who has not read his first book, the six topics are well chosen and cannot fail to excite. There have also been some significant new developments about which Casti writes in a well-practised and easy style. The reader may even be stimulated to go and buy the "prequel" -which is presumably one purpose of this book.

Tony Hey is professor of computation, University of Southampton.