The paper argues that in the Critique of Pure Reason Kant develops two anti-sceptical strategies. In the Fourth Paralogism (CPR A) he believes himself able to refute the sceptic by demonstrating that external perception is immediate. This strategy is rather unconvincing. In the Refutation of Idealism (CPR B) Kant promotes the material dependence of inner sense on outer sense. I show that Kant’s argument for material dependence has been widely overlooked, even though it is the strongest argument against external world (...) scepticism he develops, since it anticipates mental content externalism while preserving transcendental idealism and empirical realism. (shrink)