psychologism

The theory that philosophical problems are really questions of fact about the workings of the human mind, to be investigated by psychology. The theory was developed in the 19th-c by German philosophers. It was applied by Mill to the case of logic, but was strongly resisted by Frege and Husserl.

Psychologism is a generic type of position in philosophy according to which psychology plays a central role in grounding or explaining some other, non-psychological type of fact or law. The most common types of psychologism are logical psychologism and mathematical psychologism.

Logical psychologism is a position in logic (or the philosophy of logic) according to which logical laws and mathematical laws are grounded in, derived from or explained by psychological facts (or laws). Psychologism in the philosophy of mathematics is the position that mathematical concepts and/or truths are grounded in, derived from or explained by psychological facts (or laws).

John Stuart Mill seems to have been an advocate of a type of logical psychologism, as were many Nineteenth-Century German logicians such as Sigwart and Erdmann. The "Prolegomena" is considered a more concise, fair, and thorough refutation of psychologism than the criticisms made by Frege, and also it is considered today by many as being a memorable refutation for its decisive blow to psychologism. Donald Gillies criticized the radical position taken by Popper of rejecting all forms of psychologism, because it is impossible not to justify scientific theories, at least partially, on experience.