  For Rickert epistemology or Erkenntnistheorie (‘theory of knowledge’) has to be the point of departure and the systematic foundation of philosophy as a whole. He often uses interchangeably the words “logic” (Logik), “theory of knowledge” (Erkenntnistheorie), “methodology” (Methodologie), “theory of truth” (Wahrheitslehre) and “theory of science” (Wissenschaftslehre). (See for instance Rickert 1986, 19; Rickert 1909, 170.) This is because ultimately all these phrases refer to one and the same problem, i.e., the problem of the validity of thought and the principles on which valid thought rests. Erkenntnistheorie, therefore, is his preferred phrase because it makes this fundamental problem most explicit.