The notion that the Critique of Pure Reason is the enactment of a critique of reason by itself has itself been subject to a ‘peculiar fate’. The title of Kant's great work would appear to carry the suggestion of an internal connection between the powers of self-consciousness (or ‘apperception’) discovered within the pages of the Transcendental Analytic, and the very idea of a ‘self-critique’ of reason. The notion of a self-critique of reason entails that the critique be immanent: if reason is to fully criticise itself, it can allow nothing beyond itself, i.e. beyond reason, into the process. This notion of immanent self-critique seems to echo the discovery and elaboration of the ability of consciousness to be self-reflexive. The reflexivity of Kant's critical project appears to be internally related to the reflexivity of self-consciousness that forms the centre of gravity for Kant's ‘Copernican turn’. Perhaps the reflexivity Kant discovers in the ‘transcendental unity of apperception’ is even realised in the self-critique of reason. This would allow for the crucial possibility that critique can itself be internally justified at a properly metacritical level.

Nevertheless, the fact is that all of the post-Kantians, from Reinhold, Schulze and Fichte, to Schelling and Hegel, claimed that Kant failed to realise the project of the self-critique of reason. Unanimously, they argued that Kant's analysis of the limits of knowledge had not been able to account for the kind of knowledge necessary for the production of the Critique itself, and that therefore his account of these limits was flawed.