Jaspers and Popper have nothing in common beyond the legacy of Immanuel Kant's philosophy. Popper dismisses Jaspers 'existentialism' as nihilistic and historicist; Jaspers never cites Popper. Jaspers describes Kant as 'the philosopher for me'; Popper is an unorthodox Kantian whose critical rationalism put the finishing touch to Kant. For Kant, knowledge is not a simple copy of reality, but begins with reason's questioning. Jaspers and Popper too insist that theory has priority over observation. For Jaspers, 'there is already theory in every fact'; for Popper, 'every statement has the character of a theory'. Science begins with metaphysical Ideas which become scientific when tested in experience. They differ in Popper's rejection of induction in favour of falsification, while Jaspers tacitly accepts induction.
Keywords: Jaspers; Kant; Popper; legacy; psychopathology; theory and existentialism.