Bohr’s Como Argument: Complementarity and the Problem of Causality
This and the following chapter consider Bohr’s new ways (plural) of thinking about quantum phenomena and quantum theory in terms of complementarity that emerged in the wake of Heisenberg’s discovery of quantum mechanics and then of the uncertainty relations. Bohr’s thought on these subjects underwent several changes even at the earlier stages to be discussed in these two chapters, and then was further refined in the wake of EPR’s argument. The first change is the shift from Bohr’s pre-complementarity view of quantum theory in the wake of Heisenberg’s 1925 discovery of quantum mechanics to his view following Schrödinger’s wave mechanics, Dirac’s and Jordan’s transformations theory, and Heisenberg’s uncertainty relations—developments that were instrumental to the invention of complementarity, introduced in the Como lecture in 1927. This change will be discussed in this chapter. The second change, discussed in Chapter 7, was marked by Bohr’s rethinking of the question of causality in quantum theory and occurred under the impact of his exchanges with Einstein in 1927. Section 6.1 gives an introductory discussion of the developments of Bohr’s thought and of the concept of complementarity. Sections 6.2 and 6.3 offer an analysis of the Como lecture. Section 6.3 also critically examines some of the problematic implications of the Como argument, in particular those concerning quantum causality. Section 6.4 considers, from the same critical perspective, the arguments concerning quantum causality offered—in part following Bohr’s Como argument—by Dirac, Heisenberg, and von Neumann.