Krisis der Wissenschaften (crisis of the sciences) - The then widespread phenomenon of productive revolutions prompting the revision of the basic concepts of the various sciences, and especially philosophy, is first discussed in the opening paragraph of the Kassel lectures of April 1925 and reiterated in GA20   (GA20  , § 1), GA21   (GA21  , § 3), BT (SZ  , § 3), and GA25   (GA25  , § 2b). [Kisiel  ]