The Beginning of Infinity: Explanations That Transform the World, David Deutsch, Viking Press, New York, 2011. $30.00 (487 pp.). ISBN 978-0-670-02275-5
David Deutsch’s idea of a universal quantum computer and his demonstration that quantum interference can give it more power than a classical one are major and lasting contributions to science. With The Beginning of Infinity: Explanations That Transform the World, Deutsch applies his broader views on the nature of science and of rational thought to a wide range of questions. What is good science, and what kind of society fosters it? Will we create artificial intelligence, how will we know if we have, and should the prospect worry us? How should we evaluate political institutions? Is sustainability a goal we should strive for? How long will human civilization exist? Are there limits on what we can come to know? These are just a sampling.
The book’s theme is the universality and unlimited problem-solving ability of the explanation-seeking faculty of reason. According to Karl Popper, whose epistemology underlies Deutsch’s approach, knowledge consists of explanations: conjectures about how the world is that entail the phenomena to be explained. Good explanations are fragile in that it is difficult to perturb them and yet retain their explanatory power. Moreover, they facilitate understanding and prediction of varied phenomena and survive systematic attempts to falsify them by checking their implications against reality. Though compatible with and influenced in its essence by universal physical law, the reasoning required to arrive at good explanations is neither parochially human nor reducible to physical terms. For Deutsch, the process of explanation through reason, if we embrace it, promises an infinite future in which even in areas like philosophy, art, politics, and ethics, problem after problem is solved and further problems continue to be generated.
Deutsch’s conclusions are often sweeping. He argues that all regularities in nature have explanations, and therefore problems are solvable; if we do not solve them, it is because we failed to acquire the requisite knowledge. Yet he also argues that new problems will always arise. Therefore, he concludes, “sustainability,” theoretically speaking, is a chimerical notion, aimed at stasis that will lead to death.
Dozens of such provocative arguments will hold the reader’s interest. His skepticism about the Turing test for artificial intelligence is nicely argued, and the rest of his discussion of machine intelligence and creativity is engaging. So are his comments on anthropic reasoning in cosmology and elsewhere. The proposal that a good piece of music or art, like a scientific explanation, is “hard to vary” is interesting, but I’m not fully convinced. In any case, the general point that similar criteria may be used to evaluate scientific hypotheses and works of art is a valuable one. Deutsch’s standard discussion of mathematical infinities segues into a lovely illustration of how physical law affects computational and perhaps reasoning power. And his argument that social science must acknowledge reason as active in human affairs is well taken, though Deutsch may jump too quickly to conclusions from it.
Deutsch’s view that objective correctness is possible in areas outside science is appealing. And his suggestion that Popperian explanation underwrites that possibility is intriguing, but may overemphasize the importance of explanations as opposed to other exercises of reason. A broader, more balanced perspective may be found in the writings of Roger Scruton, Thomas Nagel, and others. Less appealing is Deutsch and Popper’s denial of the validity of inductive reasoning; if this involves a denial that evidence can increase the probability of general statements such as scientific laws, it is deeply problematic. To appreciate the nature and proper role of induction, one should also read such Bayesian accounts as Richard Jeffrey’s Subjective Probability: The Real Thing (Cambridge University Press, 2004) and John Earman’s Bayes or Bust? A Critical Examination of Bayesian Confirmation Theory (MIT Press, 1992).
Deutsch and Popper also oppose instrumentalism and physical reductionism but strongly embrace fallibilism. An instrumentalist believes that particular statements or entities are not literally true or real, but primarily useful for deriving predictions about other matters. A reductionist believes that they have explanations couched in the terms of some other subject area, often physics. Fallibilism is the view that our best theories and explanations are or may well be false. Indeed many of the best have already proved not to be strictly true. How then does science progress? Our theories approximate truth, and science replaces falsified theories with ones closer to the truth. As Deutsch puts it, we “advance from misconception to ever better misconception.” How that works is far from settled. This seems to make premature Deutsch’s apparent dismissal of any role for instrumentalist ideas, and his neglect of pragmatist ones, according to which meaning and truth have largely to do with how statements are used and whether they are useful.
For some of Deutsch’s concerns, prematurity is irrelevant. But fallibilism undermines some of his claims—for example, that the quantum multiverse theory is a simple consequence of saying the Schrödinger equation is true and that instrumentalism about the quantum wavefunction has the same defects as a more thoroughgoing instrumentalism about scientific theories. The apparently incompatible accounts of the world given by general relativity and quantum theory and the existence of multiple formulations of quantum theory probably sharpen these points. On these matters, and some others, Deutsch neither gives an adequate overview of current thinking nor does justice to alternatives. The treatment of quantum theory in chapter 12, “A Physicist’s History of Bad Philosophy,” illustrates this, and the treatment of 20th-century philosophy in the same chapter is close to caricature. With respect to philosophy of science, W. H. Newton-Smith’s The Rationality of Science (Routledge, 1981) and James Ladyman’s Understanding Philosophy of Science (Routledge, 2002) could provide a corrective that also puts Popperian thought in context.
The Beginning of Infinity is written clearly and is intended for a general audience. But it is also well worth reading by physicists interested in how our discipline fits into the spectrum of human activity or in questions about the future of humanity. The book is so wide-ranging and dense that evaluating its arguments—many of which seem persuasive—is difficult to do in one reading. But I strongly recommend this sprawling, sometimes frustrating, often engrossing book to readers willing to make the critical and creative effort to understand and evaluate its ambitious and often quite philosophical arguments.
