ABSTRACT
Consideration of the classic measurement paradox of quantum mechanics raises the question: What is the relationship between acceptable theories of the physical world at different levels? It is suggested that it is similar to the relationship between maps of different types and that, while theories at different levels need not be derivable from one another, they must at least be mutually consistent in their predictions. The relationship between quantum mechanics, in its standard interpretation, and classical physics fails this test. Existing attempts to resolve the measurement paradox are briefly reviewed, and it is suggested that one avenue has been insufficiently explored; namely, the possibility that the complexity of a physical system may itself be a relevant variable which may introduce new physical principles. Possible reasons for this lacuna are discussed, and it is pointed out that some of the relevant questions are now within the reach of an experimental test.
In this essay I shall try to defend three claims. The first is that the classic quantum measurement paradox, so far from being a non-problem, is a sufficiently glaring indication of the inadequacy of quantum mechanics as a total world-view that it should motivate us actively to explore the likely direction in which it will break down. The second is that, as a consequence of ingrained reductionist prejudices and perhaps to some extent of sociological factors, we may have been looking in precisely the wrong direction. And the third is that we are already at the threshold of some very significant experiments in what just might turn out to be the right direction. The third claim is one which I have discussed rather extensively elsewhere, so I will deal with it here rather briefly, without much technical detail.
