The Problem of Measurement

Abstract

The last few years have seen a revival of interest in the conceptual foundations of quantum mechanics¹. This revival was stimulated by the attempts to alter the probabilistic interpretation of quantum mechanics. However, even when these attempts turned out to be less fruitful than its protagonists had hoped,² the interest continued. Hence, after the subject had been dormant for more than two decades, we again hear discussions on the basic principles of quantum theory and the epistemologies that are compatible with it. As is often the case under similar circumstances, some of the early thinking had been forgotten; in fact, a small fraction of it remains as yet unrediscovered in the modern literature. Equally naturally, some of the language has changed but, above all, new ideas and new attempts have been introduced. Having spoken to many friends on the subject which will be discussed here, it became clear to me that it is useful to review the standard view of the late “Twenties,” and this will be the first task of this article. The standard view is an outgrowth of Heisenberg’s paper in which the uncertainty relation was first formulated.³ The far-reaching implications of the consequences of Heisenberg’s ideas were first fully appreciated, I believe, by von Neumann,⁴ but many others arrived independently at conclusions similar to his. There is a very nice little book, by London and Bauer,⁵ which summarizes quite completely what I shall call the orthodox view.