Edmund Husserl began as a mathematician; he wrote his doctorate on the theory of functions and only then turned to philosophy. *Logische Untersuchungen* (Logical Investigations) appeared in two volumes in 1900-1901 in Halle. The book is a sharp critique of the then-dominant tendency of 'psychologism' — the view that the laws of logic are the natural laws of the mind.

For Husserl, the truth of the proposition 2 + 2 = 4 does not depend on anyone's thinking it. The laws of logic are not cognitive facts but ideal objects; they differ in kind from psychological laws. The first volume establishes this view. The second volume is the constructive part: it proposes a detailed description of the 'intentional' structure of consciousness (intentional in the technical sense — directed toward something). When we think, we always think of *something*; when we see, we see *something*. Consciousness is not an empty vessel but always actively directed toward content.

To describe this intentional structure, Husserl developed the 'phenomenological method': describe our experiences as they appear to us, without judging their reality — a move he calls *epoché* (bracketing). The slogan 'back to the things themselves!' (Zu den Sachen selbst!) comes from here.

Phenomenology became one of the most productive movements of twentieth-century philosophy. Husserl's students included Heidegger, Edith Stein, and Eugen Fink; among those he influenced were Sartre, Merleau-Ponty, Levinas, and Patočka. Modern cognitive science returned to the phenomenological tradition from the 1990s on, especially through 'enactive' and 'embodied mind' theories.

Husserl retired from the University of Freiburg in 1928; under Nazi laws he was barred from his own library as a Jew, and after his death his manuscripts were smuggled to Louvain by the intervention of a Belgian Franciscan, Herman Leo Van Breda, who saved them from destruction.