 Kant’s rejection of the more specialized branches of metaphysics is grounded in part on this earlier claim, to wit, that any attempt to apply the concepts and principles of the understanding independently of the conditions of sensibility (i.e., any transcendental use of the understanding) is illicit. Thus, one of Kant’s main complaints is that metaphysicians seek to deduce a priori synthetic knowledge simply from the unschematized (pure) concepts of the understanding. The effort to acquire metaphysical knowledge through concepts alone, however, is doomed to fail, according to Kant, because (in its simplest formulation) “concepts without intuitions are empty” (A52/B76).