Otto Selz regarded psychology as the connecting element between the positivism pursued by natural scientists educated in philosophy and the metaphysics (as defined by Fichte, Hegel) pursued by philosophers applying an approach based on humanities. In his doctoral dissertation about “Die psychologische Erkenntnistheorie und das Transzendenzproblem” (“The psychological theory of knowledge and the problem of transcendence”) (doctoral supervisor Lipps in Munich), he tried to develop his own theory of knowledge by engaging in the theories of Locke, Barkley, and Hume and came to the conclusion that psychology as a biological science has to apply the methods of the natural sciences. Therefore, in principle, Otto Selz acknowledged the propositions of positivism. He regarded psychology as a life science (hence, different from humanities and natural sciences) and therefore as part of the “legal sciences”, although mathematical formulas cannot be applied to the same extent as in “exact sciences”.
Selz’ most important scientific contributions concerned questions of the psychology of thinking. After his doctorate, Selz became a student and colleague of Külpe, founder of the Würzburg School (click here for information on Adolf-Würth-Center for History of Psychology) in Bonn. The school’s main objective was the rejection of Aristotle’s theory of associationism (especially the explanation of deliberate thinking processes by the associative connection of conceptions according to the principle of contiguity) and its propositions which had been prevalent until then. In Bonn, Selz started to conduct empirical research on his work “Über die Gesetze des geordneten Denkverlaufs” (“On the laws of ordered thinking”), that later on became his habilitation thesis. By seeking to control the method-dependent “falsification” of data through procedures for the systematic variation of task settings, interrogation modes, and recording, he was instrumental in the development of methods for the analysis of thought processes (with a focus on introspection under experimental conditions).
However, the scientific relevance of the work of Otto Selz would be misjudged if he was merely classified as a representative of the Würzburg School. He further developed the theories of the Würzburg School by attempting to integrate the human nature of setting oneself an aim and pursuing a task (= motivation) as well as the varied cognitive performance of the human being, starting from basic orientation instructions to productive thinking, into a comprehensive theory. Selz regarded human thinking as a continuum of reproductive and productive operations, namely “sample actions”. According to him, productive thinking is triggered when what Selz calls a reproductive update of knowledge is not expedient. Thinking is not equal to possessing knowledge but can be compared to the possibility of applying knowledge including finding means. Within this context, Selz is primarily interested in the methodology applied by the individual during the thought process. Seebohm (1970, p. 54 et seqq.) summarized the most important findings of Selz’ psychology of thinking and classified them in seven propositions:
In his theory of thinking, Selz expressed concepts that are of fundamental importance to modern approaches, such as the schema theory (see Herrmann, 1982) and theories of artificial intelligence or problem solving theories. His description of thought processes long before computers were invented bears a strong resemblance to the principles later established by computer simulations. Without (explicitly) mentioning Selz, his methods and propsals about pedagogically “raising the intelligence level” (“Versuche zur Hebung des Intelligenzniveaus”, 1935) deducted from the theory of thinking, are recently seized within models regarding the “hierarchy of learning” and the “testing-the-limits” approach.
It was before 1920 that Selz formulated his most essential ideas on thinking as a process of interrelated operations following strict laws. In later years, especially after 1930, he mainly dealt with the inner structure of these operations, i.e. with the “phenomenological structural principles” determining the possibilities for dynamic thinking processes. In his works on the phenomenology of space, he also attempted to analyze the conditions of perception, as they are similarly described in the gestalt theory. For the theoretical elaboration of his basic concept that we essentially perceive “phenomena of increase” and “defined qualities” (e.g. space, time, sound, color), he increasingly used mathematical considerations and, on the other hand, tried to interpret geometrical axioms in terms of the psychology of perception.
After being forced into early retirement due to his Jewish ancestry in 1933, Otto Selz was was largely cut off from scientific contacts and prevented from disseminating his research work. From 1934 on, he was merely able to publish six relatively short articles (one of which was published posthumously by Révész). The unpublished manuscripts on questions of phenomenological structural principles (about 4500 pages, some of them handwritten) found in his estate, show the tirelessness with which he kept working on his theory despite political threats and limited possibilities. Because of the political circumstances his work is hardly known today, even among German researchers. Especially his works on the phenomenology of space, written after his retirement, have been nearly forgotten, although Révész described them as “going far beyond the boundaries of psychology in their significance.”