 The directedness towards a goal which Natorp claims is implied by “method” illuminates one of two  senses[19]  in which his philosophy is idealistic, namely that science (and the other activities of culture) are guided by regulative ideas or limit-concepts (Grenzbegriffe). Ideas, as Kant argues in the Transcendental Dialectic, are a priori concepts whose source lies in pure reason alone. Their only legitimate—though indispensable—theoretical use is to regulate the understanding’s cognition of objects: reason sets down the conditions under which the understanding’s activity will have achieved its ideal completion in the systematic interconnection of its cognitions, i.e., in an ultimate science. Reason thereby offers the understanding a rule—viz. maximal scope and maximal internal systematicity—against which any actually achieved system of science must be measured; and because human finitude makes it impossible in principle for any actual system to attain the ideal maximum, reason also spurs the understanding on towards ever new discoveries and  reorganizations.[20] 