In his 1948/1949 Gifford lectures the Danish physicist Niels Bohr (1885–1962) suggested that theologians make more use of the Complementarity Principle. Articles in Zygon: Journal of Religion and Science from 1966 and elsewhere advocate and also oppose such use in regard to both theology and the relation of science and religion (Reich, 1994).
Bohr had introduced complementarity in 1927: "The very nature of the quantum theory thus forces us to regard the space-time co-ordination and the claim of causality, the union of which characterizes the classical theories, as complementary but exclusive features of the description" (Bohr, p. 115). Thus, complementarity here means to keep distinct what has traditionally been merged. In contrast, the complementarity of the particle-like and the wave-like behavior of light brings together "contradictory" models that traditionally are regarded as excluding each other.
A definition of complementarity that is applicable to both physics and theology reads as follows: Complementarity refers to the possibility that the same entity/phenomenon manifests itself in distinct, categorically different ways. All the differing manifestations need to be described and explained, and be part of an overarching theory of the entity/phenomenon, but not all occur in the same spatial, temporal, or situational context, respectively. Unfortunately, the meaning of the terms complementarity and complementary changes in everyday use (e.g., we are not opposed to or competing with each other but are complementary), as well as in communication theory (in contrast to symmetrical communication between same-level partners, complementary communication takes place between a superior and an inferior position), and in psychotherapy (in a complementary relation between client and psychotherapist the client's wishes regarding mutual love or hate and dominance or subjection are met; in an anti-complementary position none are met).
Given such a difficulty, why nevertheless search for complementarity in regard to science and religion? Because it opens up a logical possibility not covered by the traditional relationships (conflict, independence, dialogue, and integration) as defined by classical logic (Reich, 1996). That logic is binary: If the choice is between A and B, and A is correct, then B must necessarily be wrong. Genuine complementarity involves a trivalent logic, articulated by Hugo Bedau and Paul Oppenheimer in 1961 (compatible, incompatible, and noncompatible), which allows for a context-dependence of the respective explanatory powers. For instance, whereas both science and religion can contribute to the understanding and the significance of the origin and the evolution of the universe, science contributes more to an explanation of what actually happened, and religion to what it means for human living.
Complementarity as defined above involves ontology, epistemology, logic, and methodology. Ontologically, a meta-relation ( entanglement as described in quantum physics by Werner Heisenberg's principle of indeterminacy) is posited between the class of contents/meanings pertaining to science and the class of contents/meanings pertaining to religion. For example, a person to whom God entrusts a mission (religion) also receives the capacity (science) to carry it through. The epistemology calls for ascertaining that the statements concerning science and religion are co-extensional, that is, they refer to the same entity/phenomenon. The logic has already been indicated. And finally, the methodological issue implies that science and religion/theology each use their own methods. From such a perspective one is led to conclude that complementarity cannot be looked for in science and religion tout court, but (if at all) in selected issues (Reich, 2002).
See also Physics, Quantum; Science and Religion, Models and Relations
bedau, hugo, and oppenheim, paul. "complementarity in quantum mechanics." synthese 13 (1961): 201–232.
bohr, niels. collected works, ed. e. rüdinger. vol. 6: the foundation of quantum physics i (1926–1932), ed. j. kalckar. amsterdam: north holland publishing company, 1985.
reich, k. helmut. "the relation between science and theology: a response to critics of complementarity." in: studies in science and theology, eds. george v. coyne and karl schmitz-moormann. vol. 2: origins, time, and complexity. geneva, switzerland: labor et fides, 1994.
reich, k. helmut "a logic-based typology of science and theology." journal of interdisciplinary studies 8, nos. 1–2 (1996): 149–167.
reich, k. helmut. developing the horizons of the mind. relational and contextual reasoning and the resolution of cognitive conflict. cambridge, uk: cambridge university press, 2002.
k. helmut reich
com·ple·men·tar·i·ty / ˌkämpləmenˈtaritē/ • n. (pl. -ties) a complementary relationship or situation: a culture based on the complementarity of men and women. ∎ Physics the concept that two contrasted theories, such as the wave and particle theories of light, may be able to explain a set of phenomena, although each separately only accounts for some aspects. ∎ Law the principle that jurisdictions will not overlap in legislation, administration, or prosecution of crime.