Before proceeding now to the last part of our analysis of Kant's attempt to move from a theory of experience to a presentation of a structured system, let us stress one point pertaining to the Marburg School's interpetation of Kant: Cassirer, an outstanding representative of that School, took the concept of the thing in itself and showed that that concept undergoes different interpretations in the different and consecutive parts of the doctrine of The Critique of Pure Reason. This interpretation, to be sure, has been closely tied up with the systematic attempt of the School to do away with the realistic residuum inherent in the notion of the thing in itself. We are now about to show — by way of an analysis, and not for the sake of a systematic attempt to resolve the dilemmas inherent in Kant — that the notion of substance is a kind of Ariadne thread which can be traced in the different parts of the doctrine.