Anti-psychologism

In logic, anti-psychologism (also logical objectivism or logical realism) 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 concept of an anti-psychologistic approach to logic originated in the work of Bernard Bolzano.

The concept of anti-psychologism was further developed by Gottlob Frege (the most famous anti-psychologist of logic), and has been the centre of an important debate in early phenomenology and analytical philosophy.

The psychologism dispute (German: Psychologismusstreit) 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).

Psychologism was defended by Theodor Lipps, Gerardus Heymans, Wilhelm Wundt, Wilhelm Jerusalem, Christoph Sigwart, Theodor Elsenhans (), and Benno Erdmann.

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. Psychologism was criticized in logic also by Charles Sanders Peirce whose fields included logic, philosophy, and experimental psychology, and generally in philosophy by Maurice Merleau-Ponty who held the chairs of philosophy and child psychology at the University of Paris.

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