In 1792 Schulze-Aenesidemus criticised Kant for this very recognition of apriorism (op. cit., pp. 56,141, etc.) and of the thing-in-itself. We sceptics, or followers of Hume, says Schulze, reject the thing-in-itself as being “beyond the bounds of all experience” (p. 57). We reject objective knowledge (p. 25); we deny that space and time really exist outside us (p. 100); we reject the presence in our experience of necessity (p. 112), causality, force, etc. (p. 113). One cannot attribute to them any “reality outside our conceptions” (p. 114). Kant proves apriority “dogmatically,” saying that since we cannot think otherwise there is therefore an a priori law of thought. “This argument,” Schulze replies to Kant, “has long been utilised in philosophy to prove the objective nature of what lies outside our ideas” (p. 141), Arguing thus, we may attribute causality to things in-themselves (p. 142). “Experience never tells us (wir erfahren niemals) that the action on us of objective things produces ideas,” and Kant by no means proved that “this something (which lies outside our reason) must be regarded as a thing in-itself, distinct from our sensation (Gemut). But sensation also may be thought of as the sole basis of all our knowledge” (p. 265). The Kantian critique of pure reason “bases its argument on the proposition that every act of cognition begins with the action of objective things on our organs of sensation (Gemüt), but it then disputes the truth and reality of this proposition” (p. 266). Kant in no way refuted the idealist Berkeley (pp. 268-72).

It is evident from this that the Humean Schulze rejects Kant’s doctrine of the thing-in-itself as an inconsistent concession to materialism, i.e.,to the “dogmatic” assertion that in our sensations we are given objective reality, or, in other words, that our ideas are caused by the action of objective things (independent of our mind) on our sense-organs. The agnostic Schulze reproaches the agnostic Kant on the grounds that the latter’s assumption of the thing-in-itself contradicts agnosticism and leads to materialism. In the same way, but even more vigorously, Kant is criticised by the subjective idealist Fichte, who maintains that Kant’s assumption of the thing-in-itself independent of the self is “realism” (Werke, I, S. 483), and that Kant makes “no clear” distinction between “realism” and “idealism.” Fichte sees a crying inconsistency in the assumption of Kant and the Kantians that the thing-in-itself is the “basis of objective reality” (p. 480), for this is in contradiction to critical idealism. “With you,” exclaims Fichte, addressing the realist expositors of Kant, “the earth rests on the great elephant, and the great elephant rests on the earth. Your thing-in-itself, which is only thought, acts on the self!” ( p. 483).