_ Source: _Page Count 25 This is a pre-print. Please cite only the revised published version. This paper presents an original, ambitious, truth-directed transcendental argument for the existence of an ‘external world’. It begins with a double-headed starting-point: Stroud’s own remarks on the necessary conditions of language in general, and Hegel’s critique of the “fear of error.” The paper argues that the sceptical challenge requires a particular critical concept of thought as that which may diverge from reality, and that this (...) concept is possible only through reflection on situations of error, in which how things are thought to be diverges from how things really are with independent items in an objective world. The existence of such a world is therefore a necessary condition of the possibility of scepticism: such scepticism is therefore false. I defend the argument against objections from Stroud’s sceptic and others. Drawing on Heidegger, the paper concludes by indicating that the chain of necessary conditions includes practical engagement with the world. (shrink)