The key to all metaphysics : Kant's letter to Herz, 1772

Kant's 1772 letter to Markus Herz is celebrated for its marking the ‘Critical turn’ in Kant's thought, a turn that would move Kant away from the speculative metaphysics of the 1750s towards the Critical philosophy of 1781. It is here, seemingly for the first time, that Kant asks the question concerning the relationship between concepts and objects, telling his former pupil that the answer to this question ‘constitutes the key to the whole secret of hitherto still obscure metaphysics.’ For anyone interested in the development of Kant's thought this makes for exciting news since it is the posing of this question that marks Kant's first step towards the Critique and it is the answer to this question that will come to identify the ‘objective portion’ of the Transcendental Deduction, a text that already begins with a rehearsal of points raised in Kant's letter. But while the letter to Herz is clearly itself a key to what Kant sees as the ‘whole secret of hitherto still obscure metaphysics’, the question concerning concepts and objects itself poses interpretive problems that need to be addressed. Above all, one needs to ask how Kant arrived at such a question.