  At the same time, Kant's own project in the Critique of Pure Reason requires what one might call transcendental psychology, that is, the study of those faculties that are required for us to have cognition. Transcendental psychology thus differs from rational psychology insofar as the former presupposes that we have experience (albeit of a very general sort), whereas the latter is restricted to the mere concept “I think”. Thus, it would seem that many of Kant's most important claims in the Critique of Pure Reason would fall under the domain of transcendental psychology. As is well known, Kant's Critique of Pure Reason came under attack immediately after its publication (most notably by Johann Georg Hamann) for not presenting an explicit account of how we obtain knowledge of our transcendental faculties.