Edmund Husserl

Husserl founded phenomenology: the rigorous study of conscious experience from the inside, before any theory or science. His slogan, zu den Sachen selbst — to the things themselves — was a demand that philosophers describe what experience is actually like, not what materialist or psychological theories say it must be like.

His method: bracket (epoché) all assumptions about whether the world really exists "out there," and attend purely to how things appear in consciousness. Consciousness is always intentional — it is always of something, directed at an object. This structure, he believed, could be described with the precision of mathematics.

Husserl trained Heidegger as his successor and lived to see Heidegger join the Nazi party and ban him, an elderly Jewish professor emeritus, from the university library. He died in 1938. His unpublished manuscripts run to forty thousand pages. Phenomenology became the dominant continental method of the 20th century — Heidegger, Sartre, Merleau-Ponty, Beauvoir, Levinas — all of them are Husserlians in some sense.