Causality and Complementarity in Philosophy of Science 4 No. 3 pp. 289-298, July 1937 WITH On the Notions of Causality and Complementarity in Dialectica 2 No. 3/4 pp. 312-319, August 15 - Nomember 15, 1948 [BOHR’S CONCEPT OF COMPLEMENTARITY]. Niels Bohr.

Causality and Complementarity in Philosophy of Science 4 No. 3 pp. 289-298, July 1937 WITH On the Notions of Causality and Complementarity in Dialectica 2 No. 3/4 pp. 312-319, August 15 - Nomember 15, 1948 [BOHR’S CONCEPT OF COMPLEMENTARITY]


Bohr’s concept of complementarity was a key underpinning of the Copenhagen interpretation of quantum mechanics. The concept includes the idea of wave-particle duality and that wave function collapse is linked to the act of making a measurement – that every time we measure, say, an electron's position, the apparatus and the electron interact in an uncontrollable way, so that we are unable to measure the electron's momentum at the same time” (Stanford Ency. Philosophy).

In the 1st essay, Bohr makes clear that despite this “we can nevertheless achieve a unified description by ‘patching together’… apparently incompatible sorts of information about the behaviour of the object under examination which we get by different experimental arrangements [that] can clearly not be brought into connection with each other in the usual way, but may, as equally essential for an exhaustive account of all experience, be regarded as ‘complementary’ to each other” (Bohr, 1937, p. 291).

Bohr’s long struggle with wave particle duality helped him in formulating his concept of complementarity. In 1926 and 1927, Bohr watched as Heisenberg and Schrödinger struggled each sought to provide a single universal framework for the description of the observational data. They saw the choice as “essentially between a description in terms of continuously evolving wave [vs] one of particles undergoing discontinuous quantum jumps” (Stanford).

Bohr, however insisted that elements of both views were valid and needed for any complete description of the data. His way out of Heisenberg and Schrödinger’s contradiction “was to renounce the idea that [wave and particle] pictures refer, in a literal one-to-one correspondence, to physical reality” (Stanford). Instead, the applicability of these pictures was to become dependent on the experimental context. This is the gist of the viewpoint he called “complementarity” – the idea that wave and particle ‘pictures’ are mutually exclusive, but that both are essential for a complete description of quantum events (ibid).

As is well known, Bohr insisted that classical concepts were necessary for any understanding of quantum phenomena. “The use of the classical concepts is necessary, according to Bohr, because by these we have learned to communicate to others about our physical experience” (ATDN, p. 8). In the 1937 essay offered, Bohr – always both physicist and philosopher – wrote: “We require the classical concepts, not only to observe, but also to communicate experimental results. The requirement of communicability of the circumstances and results of experiments implies that we can speak of well-defined experiences only within the framework of ordinary concepts (Bohr, 1937, p. 293).

Still, Bohr was “well aware of the fact that, on pains of inconsistency, the classical concepts must be given “a suitable quantum-theoretical re-interpretation,” before they could be employed to describe” and communicate quantum phenomena (ATDN).

1948 ESSAY: While essentially a summary of philosophical issues relating to atomic physics, Bohr’s 2nd essay takes on these issues of description and communicability.

In his own words, “The quantum postulate forces upon us a new way of describing physical phenomena: In this situation, we are faced with the necessity of a radical revision of the foundation for the description and explanation of physical phenomena. Here, it must above all be recognized that, however far quantum effects transcend the scope of classical physical analysis, the account of the experimental arrangement and the record of the observations must always be expressed in common language supplemented with the terminology of classical physics” (Bohr 1948, p. 313). Item #1271

CONDITION: Two individual issues in original wrappers in fine condition in a custom clamshell box gilt-lettered at the spine and on the front board.

Price: $800.00

See all items by