— Niels Bohr, 19231 “There must be quite definite and clear grounds, why you repeatedly declare that one must interpret observations classically, which lie absolute ly in thei r essenc e. . . . It must belong to your deepest conviction—and I cannot understand on what you base it.”.

The aim of this paper is to give a systematic account of the so-called “measurement problem” in the frame of the standard interpretation of quantum mechanics. It is argued that there is not one but five distinct formulations of this problem. Each of them depends on what is assumed to be a “satisfactory” description of the measurement process in the frame of the standard interpretation. Moreover, the paper points out that each of these formulations refers not to a unique problem, (...) but to a set of sub-problems. (shrink)

Bohr’s interpretation of quantum mechanics has been criticized as incoherent and opportunistic, and based on doubtful philosophical premises. If so Bohr’s influence, in the pre-war period of 1927–1939, is the harder to explain, and the acceptance of his approach to quantum mechanics over de Broglie’s had no reasonable foundation. But Bohr’s interpretation changed little from the time of its first appearance, and stood independent of any philosophical presuppositions. The principle of complementarity is itself best read as a conjecture of unusually (...) wide scope, on the nature and future course of explanations in the sciences (and not only the physical sciences). If it must be judged a failure today, it is not because of any internal inconsistency. (shrink)

How should we read Bohr? The answer to this question is by no means clear, not least because for a long period of time Bohr has not been read but rather mythologized, and his views “almost universally either overlooked or distorted beyond recognition” (Hooker 1972, 132). Even among his readers, though, there is a general feeling of uneasiness with respect to his use of words, and wide disagreement with respect to what he really meant to say. This seems to have (...) always been the case, if we recall what Ehrenfest wrote to Bohr on July 17, 1921: “Now, dear Bohr, every person I know wails only over the fact that you write your things so briefly and compactly that one always has the greatest trouble fetching all of the ideas out of the fruit cake” (Works, 3, 623). Ehrenfest’s remark suggests that our predicament with Bohr’s thought originates in fact in his own style of writing; and accordingly, the many stories told in the doxography about Bohr’s mumbling unintelligible remarks or his endlessly rewriting each of his papers seem to point to some accidental and subjective characteristics of his: he had no deep professional knowledge of the language of philosophy, not enough time, or too much anxiety. But we could also look at Bohr’s struggle with language the other way around, in a very different way. Heisenberg, for instance, noted several times that Bohr was in the process of creating ‘a new language’. (shrink)