The Unconscious Quantum  

Victor Stenger, a physicist at the University of Hawaii, is a man with a mission. Agitated by politically motivated “anti-scientists:, money-grabbing “pseudoscientists”, and “unscientific alternative medicine…creeping into health-care systems”, he feel impelled to play his part in slaying the dragons of irrationality and metaphysics menacing present-day science. But why, after four centuries of virtually unchallenged success, should science, high intellectual ground of Western culture, traditional enemy and scourge of all forms of irrationalism, obscurantism, superstition, mysticism and unreason, need to be protected, from anti-pseudo- and un-science?

Doubtless, one answer is this very success. Spiritually unsatisfied by science and defeated by its method, many are bypassing the inevitably fruitless confrontation about evidence, proofs, statistics, repeatability, independent observation, to go the whole irrational hog and simply believe – in a New Age of witches, spells, mindreading, ESP, communing with the dead, crystal power, divine influence, spirits and so on.

But Stenger dismisses New Ageism as such as wholly meretricious and has no interest in pursuing what kind of spiritual malaise or religious hunger (or scientific hubris) it might answer to. The villains menacing science are not the ignorant, gullible populace who consume the metaphysics but their scientific priests who ought to know better. These range from physicists who use science as explicit support for various holistic and religious views to those who, out of intellectual laxity, accept metaphysics-ridden interpretations of their science, when, by being more vigilant and mindful of the issues, they need no do so.

To make good his claim – addressed to the general reader as much as to fellow physicists – Stenger presents, in The Unconscious Quantum, a detailed account of quantum theory, in which he explains as accessibly and with as little mathematical pain as he can the meaning of Schrödinger’s wave euation, the uncertainty principle, quanta, wave/particle duality, double slit experiments, the collapse of the wave function, non-locality, and so on. Nothing new in this; there are many popularizations of quantum physics which cover this core material. What distinguishes Stenger’s account is the attempt – unusual and inherently difficult – to mix popular exposition with criticism of the physics community’s interpretation of the material being exposed. He needs the reader to follow the physics while rejecting various time-honoured ways of talking about it.

The disjuncture between actual science and interpretation, between experimental procedures, observations, predictions – the facts – and the underlying theory which explains them, is nowhere greater than with Quantum Mechanics. Hailed as the most successful scientific practice ever and wielding an astonishing degree of predictive accuracy, it comes with a variety of competing theories which vie with each other to interpret the same set of quantum facts.

But, as Stenger acknowledges, in practice the majority of quantum physicists are little bothered by this, being quite content to use quantum mechanics as a cookery book and to leave it to philosophers or their more theoretically minded brethren to pronounce on theory. If pushed, however, most would offer a version of the Copenhagen interpretation first set in place by Niels bohr. The advantage of Bohr’s approach is that it systematically avoids talking about a reality underlying or behind the quantum facts; for Bohr, what you see is what there is. It does this by separating the mathematical description of pure quantum phenomena from the reality observed: the first being governed by the wave equation, the latter by the “collapse” of the wave into a physically present and measurable event. But the price it pays for this is the so-called measurement problem. Not only can it not give a satisfactory answer to the question of what constitutes a measurement, but it is unable to scotch the notorious suggestion that an individual act of consciousness is necessary for a measurement to take place. The last is, of course, fertile ground for all manner of metaphysical narratives and holisms that make Stenger shudder.

Among the alternatives to the Copenhagen interpretation two stand out: the hidden-variables theory and the many-worlds interpretation. The first, favoured by Einstein and championed by David Bohm, claims that yet-to-be-discovered hidden influences will eliminate appeals to chance in the explanation of the facts and restore the idea of an underlying reality. Unfortunately, as work by John Bell was shown, hidden variables imply a form of non-locality or action at a distance that seems to contradict relativity theory and even worse, as far as Stenger is concerned, justify an extreme form of holism where every event in the universe is connected to every other. The second, invented by Hugh Everett, requires that every time an experiment can have two outcomes an entire universe, inaccessible from the present one, is brought into being in which the unobserved (that is, “false”) outcome is true. Plainly, to anybody worried about metaphysical baggage, such ontological profligacy , not to mention unverifiability, is totally unacceptable.

Stenger’s response is to argue for an interpretation called variously “post-Everett”, “consistent histories” or “decoherent histories”. A mixture of Richard Feynman’s diagrammatic approach, a philosophically de-fanged many-worlds theory and recent theoretical work of Robert Griffiths, the theory of decoherence manages, Stenger claims, to avoid all the metaphysics of its predecessors. Whether it does, and indeed what it would mean and whether it’s possible to have a metaphysics-free physics, is, to say the least, unclear from his account. The Unconscious Quantum is an interesting, provocative, informative and impassioned attempt to rescue physics from the contemporary unscientific or anti-scientific appropriations of its softer-edged theoretical self-description. There is much good sense and enlightenment in its exposition of quantum physics as well as in its remarks about mathematics and cosmology. But the general reader will need to be very sharp about the subtle connections between quantum facts and quantum interpretations to judge how philosophically misguided physicists are, and whether the theory of decoherent histories is the answer to their unwitting metaphysical sins.


TLS December 27, 1996

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