 Perhaps the most obvious problem — and certainly one of the earliest — that Kant faces concerns the issue of the thing in itself. In order to account for the content of cognition, Kant notoriously posits a thing in itself that stands outside of the realm of possible experience yet nevertheless serves as the causal source of cognitive content. This mysterious entity was attacked most famously by Jacobi, with his accusation that one could not enter into Kant’s system without the assumption of the thing in itself, but that with such an assumption one could not remain within it. Maimon too was quick to point out that the thing in itself could not be understood realistically. Rather, Maimon argues, the thing in itself must be understood as the complete conceptual determination of an object, which can be approached only asymptotically. Against Kant’s claims about a noumenal realm of things as they are in themselves, Maimon holds that the thing in itself stands only as an object of inquiry, rather than an independent, noumenal entity: in a letter he notes that the thing in itself is “nothing other than the complete cognition of appearances. Metaphysics is thus not the study of something apart from experience, but rather merely of the limits (Ideas) of experience itself.” (in Ehrensperger (2004), 250–1) As such, while Maimon agrees with Kant that since we are finite beings the thing in itself is in fact beyond the realm of possible experience, this does not imply that the thing in itself cannot in principle be an object of cognition.