Bohr recommended complementarity as a criterion of completeness for explanations of quantum phenomena. To explain fully the single-slit diffraction of electrons, for instance, one must append two mutually exclusive pictures of the behavior of the electrons between the diaphragm and photographic plate. The two pictures are not applied arbitrarily. Spatiotemporal description is appropriate given a rigidly mounted diaphragm. Causal interaction—via energy/momentum transfer—is appropriate given a movable diaphragm. The biologist who studies an animal's behavior in a particular ecosystem cannot perform the dissections and chemical analyses to uncover the underlying physiological changes within the animal without compromising the original study. Bohr maintained that every experimental arrangement with which one could study the behavior of the atoms constituting an organism will exclude the possibility of maintaining the organism alive. Self-preservation and self-generation are processes fundamental to living organisms. Bohr maintained that the "notion of life" is an "element for which an explanation is neither possible nor required".
Bohr recommended complementarity as a criterion of completeness for explanations of quantum phenomena. To explain fully the single-slit diffraction of electrons, for instance, one must append two mutually exclusive pictures of the behavior of the electrons between the diaphragm and photographic plate. The two pictures are not applied arbitrarily. Spatiotemporal description is appropriate given a rigidly mounted diaphragm. Causal interaction—via energy/momentum transfer—is appropriate given a movable diaphragm. The biologist who studies an animal's behavior in a particular ecosystem cannot perform the dissections and chemical analyses to uncover the underlying physiological changes within the animal without compromising the original study. Bohr maintained that every experimental arrangement with which one could study the behavior of the atoms constituting an organism will exclude the possibility of maintaining the organism alive. Self-preservation and self-generation are processes fundamental to living organisms. Bohr maintained that the "notion of life" is an "element for which an explanation is neither possible nor required".
The analogical extensions of Niels Bohr's principle of complementarity to the disciplines of biology, psychology, and theology are ineffective. It has been argued, moreover, that the principle of complementarity is ineffective within quantum theory itself. Bohr supported the claim that complementary pictorial-level interpretations are necessary for the explanation of quantum phenomena by invoking a correspondence argument. Henry Margenau criticized Bohr for recommending that physicists accept an irreconcilable dilemma, the horns of which are complementary "descriptions" in terms of classical observables and causal accounts in terms of abstract states. In his various publications, Margenau created a number of diagrams to represent the confirmation process. He agreed with P. W. Bridgman that operational definitions provide important links between constructs and the results of instrumental procedures. Despite Margenau's protest, many scientists in the 1930s were receptive to the idea that pictures of classical particles and waves are needed to complete the interpretation of quantum phenomena.
Abstract The vitalism-mechanism controversy was a preoccupation of Niels Bohr’s father, a professor of physiology at the University of Copenhagen, and a frequent topic of discussion at the family residence. While the terms are now archaic, the distinction between a living organism, which must interact with its environment, and a detailed scientific description of that organism, which must treat the system as isolated or isolatable, remains ambiguous. Bohr dealt with fundamental ambiguities in biology in the same way that he dealt with fundamental ambiguities in quantum physics-by analyzing the conditions for observation required for unambiguous description and avoiding appeals to extra-scientific or metaphysical constructs.
Niels Bohr accepted the distinction stressed by Immanuel Kant and others between the awareness of an object and the awareness of being aware of that object. He noted that one of the "epistemological implications" of the success of quantum theory is the necessity of directing attention to the "placing of the subject-object distinction". Causal pictures and vitalistic pictures, like particle pictures and wave pictures in quantum theory, are interpretations that supplement each other. These pictures are complementary in the sense that both types of picture are required for completeness. This is the case both in quantum physics and psychology. The mutual exclusivity of interpretations is a cornerstone of the principle of complementarity, as it is applied within quantum theory. Bohr's analogical extension of the principle of complementarity to psychology is unconvincing. A more appropriate analogy to causal and vitalistic interpretations in psychology would be from fluid and particulate models of the behavior of aqueous solutions.
The views of Niels Bohr on complementarity are examined, both in physics and in other fields. N. Bohr's opinions on the relationship between physics and biology are discussed in detail. It is shown that, over a number of years, Bohr viewed as complementary the study of organisms as atomic-molecular and as integral systems. Subsequently, owing to the development of molecular biology, Bohr rejected the idea of the complementarity in principle of the stated two types of studies. The current status of the physical theory of biological phenomena is examined, and the role of synergetics in this field is noted. The so-called antireductionism is criticized. It is shown that the views of contemporary eminent theoretical biologists reveal them to be unfamiliar with physics. The very important role of physics in the further development of biology and its practical applications is emphasized.
On August 15, 1932 Niels Bohr gave opening address of International Congress on Therapy held in Copenhagen. Bohr's title was Light and Life, and his purpose was to draw attention to epistemological implications for life sciences of fundamental changes that quantum theory had brought to conception of natural law (Bohr 1933). He thought that these changes, which extend to very idea of nature of scientific explanation, were important not only for a full appreciation of new situation brought to physics by quantum theory. According to Bohr, these developments had also created an entirely new background for viewing problems of biology, especially as concerns our views on position of living organisms in realm of natural science. In particular, Bohr proposed that notion of complementarity, which he had first presented 5 years earlier at International Congress of Physics in Como, relevant also for physiological and psychological aspects of life. Bohr began his address by stating what nowadays stigmatized as reductionist credo, namely that subtle character of riddle of life notwithstanding, any scientific explanation of biological phenomena necessarily must consist of reducing description of more complex phenomena to that of simpler ones. But, Bohr continued, discovery of an essential limitation of mechanical description of natural phenomena, as revealed by recent development of atomic theory, has lent new interest to old problem of how far program of reductive biological explanations can be carried. Bohr then presented a brief historical account of rise of quantum theory in connection with study of light, which he thought is perhaps least complex of all physical phenomena. Yet, it turned out that despite its lack of complexity, phenomenon of light cannot be given a coherent mechanical explanation, inasmuch as from viewpoint of classical physical theories, the quantum of action . . . must be considered as an irrational notion. The spatial continuity of light propagation, on one hand, and atomicity of light effects on other hand, must, therefore, be considered as complementary aspects of one reality, in sense that each expresses an important feature of phenomena of light. Those aspects are complementary, because, although they are conceptually irreconcilable from a mechanical point of view, they can never be shown to be in direct, or empirical, contradiction. The reason for this that any closer analysis of either wave aspect or particle aspect of light demands mutually exclusive observational arrangements.