Quantum Theory and the Flight from Realism: Philosophical Responses to Quantum Mechanics

Popularizing books on quantum mechanics tend often to dwell on the kinds of far-out speculative theory embraced by advocates of the rival ‘many-worlds’ or ‘many-minds’ interpretations. ¹ Such theories mostly take rise from the various well-known paradoxes of QM, such as the wave-particle dualism and the so-called ‘collapse of the wave-packet’ brought about—so it is thought-by the act of observation. ² They are invoked in order to explain how all possible outcomes of every measurement can be somehow simultaneously ‘realized’, whether in the minds of different individual observers or in different worlds which branch off when the wavepacket collapses, and thereafter coexist as a multitude of parallel universes with just occasional quantum interference-effects to signal their shadowy ‘reality’. ³ Since the observer likewise splits off at every point into a series of multiple selves, each with a continuous lifeline through one such proliferating world series only, it follows that they can have no direct awareness of this omnipresent but intangible quantum ‘multiverse’ and may therefore be tempted to find the whole idea quite fantastic. Such is at any rate how David Deutsch—currently its most vigorous champion—explains both the absolute necessity of adopting ‘many worlds’ as an answer to the QM paradoxes and also the strong resistance it encounters from a commonsense-intuitive standpoint. Thus he glosses ‘quantum theory’ quite simply as ‘the theory of the physics of the multiverse’, since in his view there is just no other means of accounting for such observed QM phenomena as photon interference or deflection in Bell-type delayed-choice or multiple-path experiments. ⁴ Indeed, ‘if the best theory available to physics did not refer to parallel universes, it would mean that we needed a better theory, one that did refer to parallel universes, in order to explain what we see’ (Deutsch, p. 51).

Deutsch is an out-and-out realist with regard to these multiple coexisting parallel worlds and spends a good deal of time chastising instrumentalists for their abject evasion of the issue. In this respect he is fully in accord with Einstein, contending that it must be the aim of any adequate physical theory to describe and explain the way things stand in reality, rather than merely to ‘save the phenomena’ by proving them predictively and observationally

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