Experience by itself is not science. - Edmund Husserl

... bloße Erfahrung ist keine Wissenschaft.

To every object there corresponds an ideally closed system of truths that are true of it and, on the other hand, an ideal system of possible cognitive processes by virtue of which the object and the truths about it would be given to any cognitive subject.

First, anyone who seriously intends to become a philosopher must "once in his life" withdraw into himself and attempt, within himself, to overthrow and build anew all the sciences that, up to then, he has been accepting.