On the relevance of the idea of complementarity.
I should like to thank Christopher Rios for his fascinating historical article on the idea of complementarity in discussions about the relation between science and Christian belief ("Claiming Complementarity," PSCF 63, no. 2 : 75-84). As an octogenarian, I have had the privilege of meeting a number of the protagonists for this idea.
However, as an engineering scientist, I have often wondered whether both scientists and theologians can forget that their specialist disciplines, such as all human knowledge, concern themselves with models of reality. In engineering, such models are constructed by selecting a small number of parameters which are of special importance for the operation of a device or system. These parameters are constructs of the human mind.
Engineers have constantly to remind themselves that their models are not the actual thing. Models can never be a substitute for a full-scale test. Moreover, useful modeling requires many different models of the same object. Thus a thermodynamic model of a gas turbine does not provide information about the price of gas in its effect on the viability of a project. Engineers who ignore economic models go out of business. This does not seem to me to be due to a philosophical principle of complementarity, but to the distinction between necessary and sufficient conditions in the solution of a problem.
A fortiori even the variety of models cannot elucidate the desirability of building a gas power station which depends on its purpose in generating electricity with its social consequences. Although Bohr's principle is undoubtedly important in the context of quantum physics, it may not be relevant to discussions between theology and science. It brings to my mind a comment attributed to Francis Bacon on William Gilbert's book De Magnete, "Gilbert has attempted to construct a world using material insufficient for the pins of a rowing boat."