It has been said that while the optimist believes that we live in the best of all worlds, the pessimist knows that we do. David Deutsch's book is profoundly optimistic, but in a way that carefully avoids these extremes. His optimism is based not on Panglossian reassurance, but on a principled and passionate confidence in people's constructive inventiveness. He thinks that the potential for unlimited creativity has arisen only once, as the culmination of a process that began in the Enlightenment.
This event is pinpointed as the discovery, by Kurt Gödel and Alan Turing in the 1930s, following hints a century earlier by Charles Babbage and Ada Lovelace, of the possibility of machines that can perform any conceivable computational task. Our laptops are the first such machines to be widely available. Deutsch regards the "jump to universality" as a seminal moment in human culture, representing an idea with enormous reach. "Reach" is one of Deutsch's favourite words (with almost the largest number of entries in the book's index); it refers to a concept with implications far beyond its original context.
He rejects techno-pessimism: our imagined inability to cope with the pace and consequences of the inventions that stem from science. To illustrate this, he reports that when colour television became popular in the 1970s, a friend argued that its dependence on the rare element europium for the red phosphor would lead to society splitting into those who could afford it and those who could not - a dangerous situation originating in a technology that nobody needed.
Now we see this argument as absurd and based on a failure to anticipate the development of other kinds of colour display, such as those used in our computer screens and based on liquid crystals. The story illustrates Deutsch's distinction between prediction, rationally based on present knowledge, and prophecy, based on the inability to imagine future knowledge.
Why did the jump to universality occur in our Western society and not elsewhere? Deutsch rejects the explanations of Karl Marx, Friedrich Engels and Jared Diamond that the dominance of the West is a consequence of geography and climate, emphasising instead the distinction between open societies, where criticism and innovation flourish - Athens, for example - and closed societies such as Sparta where change is suppressed. In stressing the importance of learning through mistakes ("error correction is the beginning of infinity"), he is a follower and admirer of Karl Popper ("science as misconception").
Another example of a closed society that Deutsch cites is Easter Island's. He contrasts David Attenborough's interpretation of it - a magnificent civilisation whose failure resulted from the destruction of the environment that sustained it - with what he regards as Jacob Bronowski's more fundamental assessment of it as a society that was unable to change, with its statues like "frozen frames in a film that is running down, mark(ing) a civilization which failed to take the first step on the ascent of rational knowledge".
Like Popper, Deutsch emphasises the open-ended nature of knowledge creation. We are now just scratching the surface of understanding the world and our place in it, and we always will be ("the beginning of infinity" again). Likewise, our evolution, now proceeding at a greatly accelerated pace by cultural transmission between generations - by memes rather than genes - is only in its initial phase.
I wonder how Deutsch would classify the medieval Islamic societies, and the earlier Indian cultures, where seminal discoveries were made (in optics and mathematics, for example) centuries before they were rediscovered in the West. Perhaps their flair for innovation vanished because the brilliant individual researchers in these societies were not embedded in a critical mass of scientists, so that the culture of collaboration, so important in the later lift-off of European science, never developed.
Deutsch has made fundamental contributions to the developing technologies based on quantum information, so it is not surprising that the heart of his analysis of explanations (and the book's most difficult chapter) concerns quantum mechanics - which is, after all, currently our deepest explanation of physical reality. He favours the "many-worlds" interpretation. His "multiverse" incorporates many universes, in which every one of the possibilities in every quantum process is actualised in an unimaginably vast sequence of splittings; of these, we have direct experience only of ours.
His argument hinges on a careful deconstruction of the concept of identicalness: an analysis of classical and quantum doppelgangers, heavily dependent on the subtle and slippery notion of fungibility. Something is fungible if the identity of an individual instance of it is irrelevant: when I lend you a pound and then you pay me back, it is irrelevant that you return the same coin, and even if you do, it is meaningless to claim that it is the same pound.
Quantum particles such as electrons are sometimes fungible and sometimes not, depending on how they interact with the rest of the world. Deutsch claims that observations of interference between quantum waves demonstrate the existence of the multiverse, but admits that this is a minority view. Most physicists are unconvinced; in my opinion, postulating this infinity of entities with which we cannot communicate is the most extravagant violation of Occam's razor.
Given the emphasis on identicalness and quantum physics, I was disappointed to see no discussion of the most important manifestation of the combination of the two. The rule specifying how the waves that represent indistinguishable quantum particles such as electrons register an interchange of two of them is a mighty fact about our world. It explains the structure of the atoms in the periodic table of the chemical elements, why these are stable, how lasers work, why wires conduct electricity, and much else.
Deutsch criticises the opinion that quantum theory needs no interpretation - disparagingly described as the "shut up and calculate" school - and calls it "bad philosophy". I disagree. The principles of any currently fundamental theory cannot be explained: they are simply postulated. That is what "fundamental" means. Asking for an "interpretation" amounts to explaining the theory in terms of deeper concepts. But that would be new physics; it would be more fundamental.
I do not claim that quantum mechanics is the ultimate microscopic science; one day, it will surely be superseded, probably as the result of experiments that are incompatible with it. There are currently no such experiments, so quantum physics is the best theory we have: the fundamental one. The alternative mathematical formulations of quantum mechanics, all yielding the same predictions for experimental results, may inspire different pictures that assist our intuition in applying the theory to different phenomena, but no one of them should be regarded as privileged.
This is Deutsch at his most ambitious, seeking to understand the implications of our scientific explanations of the world. At first sight, his book looks like an intellectual smorgasbord, with short chapters - some of which could stand as separate essays - dealing with beauty in art and nature (he thinks this is absolute; I do not), the origins of morality, memes, quantum physics, computational complexity, electoral voting systems (he argues that the British first-past-the-post system is the least worst of many flawed alternatives) and artificial intelligence. But they are all linked (albeit sometimes tenuously) with his theme: the possibility of endless transformation of the world by the creation of new knowledge.
I do not agree with everything that Deutsch writes, but I enthusiastically recommend this rich, wide-ranging and elegantly written exposition of the unique insights of one of our most original intellectuals.
Michael Berry is a physicist at the University of Bristol, studying optics and quantum physics and the mathematical relationships between different levels of explanation in physics.
David Deutsch, a visiting professor in the department of atomic and laser physics at the Centre for Quantum Computation, University of Oxford, says he enjoyed chemistry at least as much as physics at school. "But I always knew that the attraction of chemistry was finite. I had my own chemistry lab at home and did experiments that make me shudder today."
He gained a bachelor's degree in natural sciences from the University of Cambridge in 1974, staying on to pursue a master's in mathematics before completing a DPhil in mathematical physics at Oxford in 1978. He took every opportunity to travel and says: "I never went to see places, only to meet interesting people. I used to write to everyone I admired and ask to see them. Often it worked."
When "the internet became seriously usable", Deutsch gradually stopped travelling. Now, he says, "it's hard to get me to go to the university, let alone anywhere else". In the 1990s, he left full-time employment as an academic to focus on consultancy, writing and giving the occasional lecture (he never gives the same talk twice).
One of the founders of quantum computing, Deutsch became a Fellow of the Royal Society in 2008.
The Beginning of Infinity: Explanations that Transform the World
By David Deutsch
Allen Lane, 496pp, £25.00
Published 31 March 2011