In
logic, anti-psychologism (also logical objectivism[1] or logical realism[2][3]) is a
theory about the nature of
logical truth, that it does not depend upon the contents of human ideas but exists independent of human ideas.
The psychologism dispute (
German: Psychologismusstreit)[9] in 19th-century German-speaking philosophy is closely related to the contemporary
internalism and externalism debate in
epistemology;
psychologism is often construed as a kind of internalism (the thesis that no fact about the world can provide reasons for action independently of desires and beliefs) and anti-psychologism as a kind of externalism (the thesis that reasons are to be identified with objective features of the world).[10]
Edmund Husserl was another important proponent of anti-psychologism, and this trait passed on to other phenomenologists, such as
Martin Heidegger, whose doctoral thesis was meant to be a refutation of psychologism. They shared the argument that, because the proposition "no-p is a not-p" is not
logically equivalent to "It is thought that 'no-p is a not-p'", psychologism does not logically stand.
Charles Sanders Peirce—whose fields included logic, philosophy, and experimental psychology[12]—could also be considered a critic of psychologism in logic.[13]
Psychologism is not widely held amongst logicians today, but something like it has some high-profile defenders especially among those who do research at the intersection of logic and
cognitive science, for example
Dov Gabbay and
John Woods, who concluded that "whereas mathematical logic must eschew psychologism, the new logic cannot do without it".[14]
Notes
^Dermot Moran, Rodney K. B. Parker (eds.), Studia Phaenomenologica: Vol. XV / 2015 – Early Phenomenology, Zeta Books, 2016, p. 75: "Husserl was an exponent of logical objectivism and an opponent of logical psychologism".
^Edgar Morscher [
de] (1972), "Von Bolzano zu Meinong: Zur Geschichte des logischen Realismus." In: Rudolf Haller (ed.), Jenseits von Sein und Nichtsein: Beiträge zur Meinong-Forschung, Graz, pp. 69–102.
^Penelope Rush, "Logical Realism", in: Penelope Rush (ed.), The Metaphysics of Logic, Cambridge University Press, 2014, pp. 13–31.
^Peirce (sometimes with
Joseph Jastrow) investigated the
probability judgments of experimental subjects, pioneering
decision analysis. He and Jastrow wrote "On Small Differences in Sensation", Memoirs of the National Academy of Sciences (1885), 3, 73–83, presented 17 October 1884, reprinted in
Collected Papers v. 7, paragraphs 21–35. Classics in the History of Psychology.
Eprint.
^Peirce attacked the idea, held by some logicians at that time, that rationality rests on a feeling of logicality, rather than on fact. See the first of Peirce's 1903
Lowell Institute Lectures "What Makes a Reasoning Sound?", Essential Peirce v. 2, pp. 242–257. See also the portion of Peirce's 1902 Minute Logic published in Collected Papers v. 2 (1931), paragraphs 18–19 and 39–43. Peirce held that mathematical and philosophical logics
precede psychology as a special science and that they do not depend on it for principles.