Complementarity principle
The by physicist Niels Bohr established complementarity principle states that two different methodological observations (descriptions) of a process ( phenomenon ) are mutually exclusive, but still belong together and complement each other. As an example from quantum mechanics , the fact that a simultaneous determination of the wave and particle character of light is not possible, but depending on the experimental arrangement, one or the other property emerges. Wave and particle properties can be described by two different, complementary observation sets ( complementary observables , wave-particle dualism ). Bohr already generalized the term complementarity to fundamental contradictions and paradoxes in other areas.
Definition by Bohr
Niels Bohr introduced the concept of complementarity at a physics congress in Como 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 characters the classical theories, as complementary but exclusive features of the description, symbolizing the idealization of observation and definition respectively. "
“According to the essence of quantum theory, we must be content with understanding the space-time representation and the requirement of causality, the union of which is characteristic of the classical theories, as complementary but mutually exclusive features of the description of the content of experience symbolize the idealization of the possibilities of observation and definition. "
Bohr thus primarily refers to the incompatibility that emerged in quantum mechanics - with the discovery of the quantum of action by Max Planck - that “a detailed causal tracing of atomic processes is not possible, and that every attempt to acquire knowledge of such processes "Bohr sees the task of developing a theory of complementarity, and already in these early essays points to a profound analogy between the concept of complementarity and the general difficulties in cognition that arise in the subject-object - The distinction is justified.
A correspondence of complementarity is found in that of Werner Heisenberg introduced in 1927, quantum physics uncertainty principle that location and momentum of a particle can not be taken simultaneously.
The physical discussion of the concept of complementarity often refers to an experimental setup called a double-slit experiment . The measurement process is a crucial condition of the experiment, because the detection or measurement of the exact path of a certain particle changes the outcome of the experiment significantly (although this effect can be reversed by a quantum eraser under certain conditions ). In contrast, the result of a measurement in classical physics is not significantly influenced by the measurement process. According to the original view, it was impossible to measure the wave and particle character simultaneously and within the same experiment. In more recent experiments, e.g. B. from the research group around Anton Zeilinger , succeeded in an experiment to "switch" between wave and particle properties of a photon pair. The property is only established through the experimental intervention in the double-gap arrangement.
Problems of interpretation
From the beginning, already in the discussion between the theoretical physicists, above all Werner Heisenberg , Albert Einstein , Wolfgang Pauli , Carl Friedrich von Weizsäcker , there were considerable difficulties in understanding Bohr's views, and since then the principle of complementarity has found numerous different interpretations (see Copenhagen Interpretation ). The important considerations include:
- The dependence of physical statements on contextual conditions , especially on the selection of the experimental investigation conditions, is postulated in agreement , with further interpretations of epistemological , ontological and logical nature following , depending on the author ;
- two elementary statements about a state of affairs are complementary if they cannot be decided at the same time;
- the test arrangement or methodology for describing one property prevents the occurrence of the properties linked to the other test arrangement.
The results from the independent, mutually exclusive experimental arrangements complement each other to form the overall picture of reality and overcome their respective “methodological blindness”.
The two paradoxical statements are also called adversarial , i.e. H. contradicting, as non-exhaustive, ie not exhaustive of the meaning content, as incommensurable , ie cannot be represented with the same unit, or incompatible , d. H. incompatible, incompatible, labeled. The frequent phrase “neither compatible nor incompatible, but incompatible” means that the statements are neither compatible nor incompatible with one another, but rather incompatible in a third way, i.e. H. complementary , are.
The most frequently mentioned defining features include:
- two experimental test arrangements selected by an investigator,
- within an explanatory physical theory that too
- two observational sentences (phenomenal sentences) that cannot be registered at the same time, i.e. that are methodically mutually exclusive, lead
- co-causal (not causally dependent on each other) and
- are co-referential and co-extensional (related to the same process)
- and are therefore referred to as complementary (incompatible).
Logical complementarity
Donald MacKay (1958) takes the point of view that complementarity does not have a physical but a logical basic meaning. The demand for complementary descriptions arises on a purely logical level, "whenever certain pairs of descriptive concepts (frequency and time, or wave-number and position) are used to characterize a mathematical function such as a train of waves."
"Two (or more) descriptions may be called logically complementary when (a) They purport to have a common reference; (b) Each is in principle exhaustive (in the sense that none of the entities or events comprising the common reference need be left unaccounted for), yet (c) They make different assertions, because (d) The logical preconditions of definition and / or of use (ie context) of concepts or relationships in each are mutually exclusive, so that significant aspects referred to in one are necessarily omitted from the other. "
As a synthesis and higher representation of two or more complementary descriptions, the principle is useful and at the same time constitutes a warning against misinterpreting such relations, i.e. to believe that these complementary determinations refer to different things, are synonymous, are not exhaustive and are contradictory.
Philosophical definition
A scientifically-based definition ( explication ) of the principle of complementarity was only attempted in 1963 by Hugo Bedau and Max Oppenheim, after they had agreed with a number of well-known physicists and theorists of science. This logical analysis takes place in “physical terms” and is based on important distinctions such as: sentences of observation and sentences of interpretation, phenomenon and interpretation, paradoxical situation and its resolution according to Bohr, incompatible (neither compatible nor incompatible) sentences.
"The purpose of this paper is to give a precise explication of the concept of complementarity in Quantum Mechanics (QM, for short) as introduced and brought to prominence by Niels Bohr. Einstein once pointed out that there was no adequate definition of this concept, and this is still true today. "
"Granted that in QM it is the phenomenon sentences which are complementary, we have seen that they (a) describe observations well-defined by reference to mutually exclusive experimental arrangements, (b) refer to co-causal objects, (c) are exhaustive , (d) are expressed in classical language, and (e) are interpreted by co-referential interpretations which are (f) in a quasi-classical language. Thus, two phenomenon sentences are complementary only if they satisfy (a) - (f). However, none of (a) - (f) is an independent condition on complementarity. "
Each of the six defining features is explained in detail and also in formal notation. The essay closes with the skeptical assessment:
"As to the application of complementarity in fields other than QM, no one to our knowledge uses a generalization of (or even a very exact analogue of) the concept of complementarity in QM at all. Eg, writers do not usually hold that the removal of a paradoxical situation - without which the need for complementarity in QM simply does not arise - is a condition on the introduction of complementarity, as we have. As a result, all examples known to us of complementarity outside QM are at best examples of non-compatibility. But non-compatibility, important as it is, is not sufficient for complementarity in QM, or elsewhere. "
Generalized complementarity principle
Bohr's generalizations
Bohr pointed to the impossibility of a strict separation of phenomena and means of observation and also referred to psychology. “We are especially familiar with the need to resort to a complementary or rather reciprocal way of describing in this sense through psychological problems” ... where “the difficulties that problems of definition and observation present in scientific investigations were recognized for a long time before such questions found current interest in the natural sciences "
The dependence of psychological findings on the research situation and the social interaction between the examiner and the research participant is a central subject of methodology in psychology (see reactivity (social sciences) ).
Bohr transferred his principle to many other areas, to questions of biology, psychology and culture, without, however, defining the assumptions assumed in the case of quantum mechanics in a corresponding way and consistently between physical (and other) observational sentences and the derived interpretative sentences differentiate (Favrholdt, 1999, Plotnitsky, 2013).
In Bohr's (1931, 1937) representations, three main meanings or levels of the complementarity principle can be distinguished (Fahrenberg, 2013):
(1) the complementarity of observations of quantum mechanical facts in the form of two related and yet mutually exclusive, i.e. H. paradoxical observation sentences about physical facts in experimental test and measurement arrangements;
(2) the complementarity of related and mutually exclusive descriptions as in the contrast between observer and observed (subject and object of perception), brain processes and psychological events, causality of brain processes and feeling of free will;
(3) the principle of complementarity as a universal attitude to knowledge and as a program that serves the unity of knowledge and sciences (according to Bohr's motto: “contraria sunt complementa” - opposites complement each other).
The distinction between (1) and (2) follows from the central role of the mutually exclusive observational sentences in the context of their objective-experimental test arrangements, as they are not given in a formally similar form neither in psychology nor in other human sciences . The criterion that the observations do not coincide spatially and temporally also remains questionable. The variety of references and examples mentioned by Bohr in relation to (2) therefore only seems to give indications of an analogy , a heuristic or a paradox .
Complementarity principle (psychology)
In the field of psychology, the vague both-and can be limited to a stricter version: the assignment of two independent reference systems that are fundamentally different in their category levels (general terms) . This view can be explained in particular with regard to the mind-body problem and the subjective and neurophysiological view of free will , but it also affects many decisions on research methodology and practice in psychology. Complementarity according to Bohr's version (2) states:
- knowledge-related (epistemological) the connection of two categorically fundamentally different approaches to knowledge (reference systems, description systems) to form a holistic view (point of view)
- an independence of the general terms as demonstrated by consciousness psychology compared to neurophysiology;
- methodologically, the operational closeness of each of these reference systems with regard to validity criteria, confirmation and falsification methods in a consistent, apparently exhaustive description, whereby the respective typical methods exclude each other, since they can usually not be used strictly simultaneously, but only alternately;
- Reality is only represented when both reference systems or descriptions are combined to form an overall picture (such as the subjective and the physiological processes during a psychophysical emotion).
The idea of complementarity is not an attempt to solve the underlying contradiction, but a mediation in methodological terms. In a specific research case, the principle would require an explicit justification if one of the two reference systems is dispensed with where it is practically possible. For the methodology of psychology and neuropsychology, it follows that the introspective-consciousness-psychological methods are on an equal footing with the biological-behavioral methods: Not either self-reports and self-assessments or physiological function and behavior measurements, but a purposeful use of both paths of knowledge. However, the principle of complementarity assumes that it is the same underlying process, the same event. In contrast to the physical phenomenon of light are in such transfers, for example, on the psychophysical process of emotion , statements on two categorical assign different levels to each other, so that empirical, definitional difficulties can set the Correlating to identify sufficient. From this critical point of view, the notion of perspectivity is preferable; H. the methodically reflected change between two coordinated perspectives.
The discussion on the principle of complementarity was philosophically expanded in particular by Hans-Ulrich Hoche (2008) to include "anthropological complementarism" and by Helmut Reich (2002) on "Relational and Contextual Reasoning and the Resolution of Cognitive Conflicts" and Harald Walach (2013) on the theory of science continued in psychology. From a philosophical and language-analytical point of view, Hoche starts with the concept of identity and explains that there is a fundamental dichotomy of the perspective of the first person and the third person, which he describes as the categorical difference , i.e. H. the conditions (perspectives) are not dual perspectives, not “two sides of one and the same condition”, they are neither numerically identical, nor are they numerically different, but they are in a complementary relationship. From a developmental psychological point of view, Reich arrives at a more general conception of relational and contextual thinking, as it can serve to solve cognitive conflicts. A complementary relationship is assumed if two statements are neither compatible nor incompatible. This condition is given in various problems, in psychology, theology and in other areas. Instead of phenomenon sentences in the narrower sense, pairs of statements (interpretation sentences) that no longer have any direct relation to an experimental set-up are examined for their compatibility.
Further generalizations and criticism
Following Bohr's example, the term complementarity was transferred to contradictions and dualisms in many areas: in biology and psychology, in pedagogy, social and cultural sciences through to philosophy and theology. There are precursors to the term and similar concepts. Often it seems to be just a fuzzy “as well as” and little more than a metaphor.
literature
- Niels Bohr: The Quantum Postulate and the Recent Development of Atomic Theory. In: Nature . (Suppl.) Vol. 121, 1928, pp. 580-590.
- Niels Bohr: Quantum of action and description of nature. In: The natural sciences . Volume 17, 1929, pp. 483-486.
- Niels Bohr: Atomic theory and description of nature . Springer, Berlin 1931.
- Niels Bohr: Causality and complementarity. In: Philosophy and Science. Volume 4, 1937, pp. 289-298.
- Niels Bohr: Atomic Physics and Human Knowledge. Vieweg, Braunschweig 1985, p. 21.
- Hugo Bedau, Paul Oppenheim: Complementarity in quantum mechanics: A logical analysis. In: Synthesis. Volume 13, 1961, pp. 201-232.
- Jochen Fahrenberg: On the theory of categories in psychology. Complementarity principle. Perspectives and change of perspective . Pabst Science Publishers, Lengerich 2013, ISBN 978-3-89967-891-8 . (online) (revised, second version)
- David Favrholdt (Ed.): Complementarity Beyond Physics (1928–1962) . Volume 10. Elsevier, Amsterdam 1999.
- Jan Faye, Henry Folse: Niels Bohr and Contemporary Philosophy. In: Boston Studies in the Philosophy of Science. Volume 153, Kluwer 1994.
- Ernst-Peter Fischer: Niels Bohr. Physicist and philosopher of the atomic age . Siedler, Munich 2012.
- Hans-Ulrich Hoche: Anthropological complementarism. Linguistic, logical, and phenomenological studies in support of a third way beyond dualism and monism. mentis, Paderborn 2008, ISBN 978-3-89785-612-7 .
- Donald MacKay: Complementarity. In: Proceedings of the Aristotelian Society Supplement. Volume 32, 1958, pp. 105-122.
- Klaus Michael Meyer-Abich: Correspondence, Individuality and Complementarity. Steiner, Wiesbaden 1965.
- Arkady Plotnitsky: Niels Bohr and Complementarity: An Introduction. Springer, New York 2013, ISBN 978-1-4614-4516-6 .
- Karl-Helmut Reich: Developing the horizons of the mind: Relational and contextual reasoning and the resolution of cognitive conflict. Cambridge Univ. Press, Cambridge 2002, ISBN 0-521-81795-1 .
- Harald Walach: Psychology. Theory of Science, Philosophical Foundations and History. 3. Edition. Kohlhammer, Stuttgart 2013, ISBN 978-3-17-022937-2 .
Individual evidence
- ↑ quoted from: Favrholdt: Complementarity Beyond Physics (1928–1962). 1999, p. XXIV, and Bohr: The Quantum Postulate and the Recent Development of Atomic Theory. 1928, p. 580.
- ↑ Bohr: Atomic theory and description of nature. 1931, p. 36.
- ↑ Bohr: Quantum of action and description of nature. 1929, p. 486.
- ↑ Meyer-Abich (1965) thinks that Bohr explicitly saw the quantum mechanical description of nature as complementary, "... whereby he again repeatedly avoided calling the terms occurring in the indeterminacy relations complementary, but only spoke of the complementary character of the quantum mechanical description of nature in express these relations. ”Meyer-Abich: Correspondence, individuality and complementarity. 1965, p. 153 f.
- ↑ Thomas J. Herzog, Paul G. Kwiat, Harald Weinfurter, Anton Zeilinger: Complementarity and the Quantum Eraser. In: Phys. Rev. Lett. 75, 1995, pp. 3034-3037, doi: 10.1103 / PhysRevLett.75.3034 (abstract).
- ↑ On the theory of categories in psychology. Complementarity principle. Perspectives and change of perspective . 2013, pp. 299-390.
- ^ McKay: Complementarity. 1958, p. 106.
- ^ McKay: Complementarity. 1958, pp. 114-115.
- ^ Bedau, Oppenheim: Complementarity in quantum mechanics: A logical analysis. 1961, p. 201.
- ^ Bedau, Oppenheim: Complementarity in quantum mechanics: A logical analysis. 1961, p. 224.
- ^ Bedau, Oppenheim : Complementarity in quantum mechanics: A logical analysis , 1961, p. 225.
- ↑ Bohr: Quantum of action and description of nature. 1929, p. 484 f.
- ↑ Niels Bohr: Biology and Atomic Physics. Lecture in Bologna. 1938; see Bohr: Atomic Physics and Human Knowledge. Vieweg, Braunschweig 1985, p. 21.
- ↑ Fahrenberg: On the theory of categories in psychology. Complementarity principle. Perspectives and change of perspective. 2013, p. 333.
- ↑ Fahrenberg: On the theory of categories in psychology. Complementarity principle. Perspectives and change of perspective. 2013, p. 368.
- ↑ Fahrenberg, 2013.