Anti-psychologism and the autonomy of logic: are the laws of logic ideal and apodictic, or are they psychological regularities?

Edmund Husserl, answered from the texts and cited to the page.

The position in brief

Logical truths are ideal, atemporal, and apodictic; psychological acts of judging are empirical, factual, and contingent.¹ The two domains cannot be conflated without category mistake. The psychologistic claim that the laws of logic are psychological regularities of thought (Mill) or laws of human reason (Sigwart, Erdmann) commits this category mistake and collapses into a skeptical relativism — for laws relative to a species (anthropologism) or to an individual (individualism) are not laws at all in the sense logic requires.²³

The validity of the principle that 2 + 3 = 5 stands by itself as a pure truth whether or not there is a world and this world with these actual things. The ideality of meaning, the apodicticity of evidence, and the apriority of logical law cannot be founded on or explained by reference to the factual-empirical nature of the psyche.⁴

Sources

1. F. A. Lange likewise said (cf. the last paragraph of the long citation from the Logische Studien, above, 28) that the factual elimination of contradictions in our judgements was the ultimate ground of logical rules. 7. Psychologism as a sceptical relativism 1. Please note that the term 'knowledge' is, in this work, not restricted, as it usually is restricted, to objects that are real. 2. Ch.

   Logical Investigations Vol 1, pp. 607–608

2. Psychologism in all its subvarieties and individual elaborations is in fact the same as relativism, though not always recognized and expressly allowed to be such. It makes no difference whether, as a formal idealism, based on a 'transcendental psychology', it seeks to save the objectivity of knowledge, or whether, leaning on empirical psychology, it accepts relativism as its ineluctable fate.

   Logical Investigations Vol 1, pp. 258–260

3. If there are such traits and laws essentially common to all men, then they make up the specific nature of man. All truth in its universal validity is therefore relative to the human species, or, more generally, to some species or other of thinking beings. If species differ, so do truths and laws of thought.

   Logical Investigations Vol 1, pp. 265–266

4. None of these acts enters the extension in question, but only 2 × 2 = 4 and alongside of it, e.g. The earth is a cube, the theorem of Pythagoras etc., and each only in the singular. The same is obviously true if one says 'The judgement S follows from the judgement P' and so in all similar cases.

   Logical Investigations Vol 1, pp. 305–306

Where the argument is made

• Logical Investigations Vol 1 (Prolegomena to Pure Logic, §§17-51) on Mill, Sigwart, Erdmann, the empiricist consequences of psychologism, anthropologism as relativism
• Husserl's review of Frege's correspondence and the 1894 Frege review of Philosophy of Arithmetic
• Ideas I §§18-21 on natural attitude vs. eidetic
• 'Philosophy as a Rigorous Science' (1911, in Phenomenology and the Crisis of Philosophy) on naturalism and historicism

How the argument was received

The Prolegomena's critique was decisive for both the analytic and continental traditions: Frege had pressed similar concerns in 1894, and the anti-psychologism shapes the entire division between formal logic and empirical psychology that the twentieth century inherited. The modern naturalizing phenomenology program (Petitot, Varela, Pachoud, Roy, eds., 1999) and the broader cognitive-science / philosophy-of-mind project ask whether phenomenology can after all be naturalized — engage seriously, distinguish firmly. Recent experimental philosophy that tests intuitions about logical principles against subject populations brushes against the same boundary, and the response is the same: the empirical question (what do subjects say?) is structurally distinct from the normative question (what is logically valid?).