1 The Nature of Human Reason: Willaschek on Kant on the Rational Sources of Metaphysics Katharina Kraus, University of Notre Dame Forthcoming in Studi Kantiani. Pre-print/Author's Original Version Abstract: In his new book Kant on the Sources of Metaphysics, Marcus Willaschek offers a hugely illuminative and rewarding interpretation of the «constructive side» of Kant’s transcendental dialectic in the Critique of Pure Reason. A central claim of the Rational Sources Account of metaphysics that Willaschek develops in this book and which he attributes to Kant is the thesis that reason itself is the subjective source of both metaphysical questions and answers to these questions. Yet, by its very nature, human reason is not capable of answering these questions properly and hence finds itself trapped in unavoidable metaphysical speculations and natural illusions. In this paper, I explore the scope and the philosophical implications of Willaschek’s Rational Sources Account. Firstly, I introduce what Willaschek calls the «tragic fate of human reason» and raise questions regarding the possibility of a supremely rational intellect. Secondly, I explore Willaschek’s account of the «nature» of human reason and detect a potential dilemma for the Rational Sources Account. Thirdly, I discuss Willaschek’s account of the proper, regulative use of reason and indicate an alternative reading that may help to mitigate the dilemma. Finally, I critically assess Willaschek’s radical reading of transcendental ideas and, again, indicate an alternative one. Key words: Kant, Metaphysics, Nature of Human Reason, Ideas of Reason, Transcendental Dialectic, Supremely Rational Intellect Academic Affiliation and Email: Department of Philosophy University of Notre Dame 309 Malloy Hall Notre Dame, IN 46556, USA E-Mail: kkraus2@nd.edu