Complementarity

Complementarity is a concept of epistemology for two ( apparently) contradictory, mutually exclusive, not reducible to one another ways of describing or experimental designs, but they are necessary in their mutual supplement an understanding of a phenomenon or state of affairs as a whole. This term had the physicist Niels Bohr introduced as complementarity in quantum physics and then applied to many areas. Therefore, the term was ambiguous and often thinks only a basic " both-and also ".

Two complementary properties belong together, provided they have the same reference, so the same " object" relate to, but are not causally interdependent. The two methods used are fundamentally different in the process and can not simultaneously, but can only be used one after the other in general.

Precursor

Precursors of this concept to identify with the intention to repeal a fundamental contradiction or a paradox, can be found:

• In Chinese philosophy, the yin- yang principle, the indissoluble bond of opposites into a whole ( Taoism );
• In theology and Christology of the divine, godlike or creaturely nature of Jesus (First Council of Nicaea, Council of Chalcedon ), the compatibility of God's love and omnipotence with the existence of evil in the world ( theodicy ), and in the definition of the relationship to the natural sciences on the question of creation and origin of the world (see Pannenberg );
• In the coincidentia oppositorum ( Nicholas of Cusa );
• In the doctrine of the two attributes of a substance doctrine ( double aspect doctrine ) of Baruch de Spinoza, according to which mind and matter are two sides of the same coin and are ( una eademque res);
• In the doctrine of psychophysical parallelism ( Gottfried Wilhelm Leibniz, Fechner );
• In the antinomies of Immanuel Kant, for example, freedom of the will and causality.

The word "complementary" is long ago to find Bohr's new coinage:

• In the logic of the relationship between two classes, one of which contains a all the elements of the other elements are not (see set theory, complement);
• In perception and sensory physiology as a complementary color;
• In psychology and psychoanalysis for the elimination of areas of consciousness, which then coexist and their content are mutually inaccessible ( William James, Sigmund Freud);
• In linguistics describes the antonym (opposite word) the complementary term;
• In social policy, in technology and the natural sciences.

Quantum physics

In quantum physics, complementarity is now usually explained using the example of wave -particle duality of light, which is used to describe an experimental set-up as a wave in the other as particles (see double -slit experiment, complementarity ). Attention is also drawn to the facts of quantum mechanics that certain complementary measures, such as the location and momentum of an electron, can not simultaneously have a precisely defined value ( Heisenberg uncertainty principle ).

Bohr has not clearly uses the term. Central is the complementary nature of the quantum mechanical description of nature that requires a new perspective on the relationship between space -time representation and the requirement of causality. Essential is the epistemological insight that quantum mechanical findings and - generalized - many scientific findings, such as in biology and psychology, depend on the chosen experimental arrangement and other examination conditions and mutually exclusive features of the description may represent. In this respect, Heisenberg's uncertainty relation for drilling only an elementary example (see complementarity ).

To what extent was Bohr in his choice of the term complementarity through the history of ideas and forerunner in philosophy and theology excited, is controversial.

Newer concepts of complementarity

Examples can be found:

• In biology, the ratio of complementary spatial molecular structures, their interaction according to the key - lock principle is a prerequisite for the fulfillment of a certain function;
• In Neuropsychology, Psychophysiology, Psychosomatic Medicine and Complementary Medicine, the relationship and the collision - related -ness of personal experience ( the intangible processes of consciousness ) and the neuronal processes, the " purely psychological " and " purely physical " factors to the explanation of health disorders and diseases;
• In ethno psychiatry by Georges Devereux describes complementarity, the complementarity and correction of various methods that have the same subject, such as the theory of an ethnocentric imperialism against the assumption of universal psychological principles or the location awareness of ethno- psychiatrist against the absolutism of partial aspects of a culture;
• In communication theory by Watzlawick the interaction of two circular patterns in communication processes, which complement each other and condition (such as teachers and students or persecutors and persecuted );
• In the economy the interaction of two currencies in local economic circuits ( complementary currency );
• In education after Jongebloed a principle to explain the phenomenon of education based on the ratio of knowledge and experience;
• In international criminal law of complementarity refers to the ratio between the International Criminal Court and national courts.

Criticism

The complementarity principle was following the pattern of Bohr, taken in different areas of science. The situation may be objected that the generalization of the original concept to other opposites in the sense of a vague both-and also delivers little more than a metaphor. The term complementarity is basically superfluous or ceiling only to contradictions. Not every pair of opposites, each dilemma or any duality could be described as complementary relationship.

Such transfers depart from major defining features of complementarity in quantum mechanics from. In general, no physical formulated observation sentences are given from experimental systems. The methods used are rarely precisely defined, and ask if they mutually exclusive or do not apply at the same time, remain open. Distinguish the ( two ) methods used generally and they might belong in categorical fundamentally different frames of reference? The existing difference or contradiction is seldom formulated in a strictly negative form, ie not paradoxical. It is no longer about incompatible, experimental coexisting observation sentences, but to interpret sentences (see complementarity ), or even just simple combinations of methods or views or interactions.

Other authors claim a heuristic, relationship -creating function and fertility of the methodological approach, which often does not assert a solution to a problem, but it is understood as an attempt at mediation. Therefore it would be useful to the understanding, more than to speak in most cases of complementary relationships and mutual supplement, or prefer the less loaded terms perspective, double perspective and perspective that are not complicated by definitions from quantum mechanics.