In this article, I wish to shed a new light on Heidegger's philosophical position toward idealism and realism. This will be accomplished through an analysis of Heidegger's account of the problem of scepticism in §43 of Sein und Zeit. Heidegger's position toward scepticism has often been overlooked or treated candidly by scholars and, as a result, misunderstood in the larger philosophical world, who frequently equated Heidegger's philosophy with some form of scepticism. By highlighting some crucial ambiguities in the unfolding of §43, I show that in Sein und Zeit Heidegger is elaborating a radical refutation of scepticism even though it will ultimately only be accomplished in the Beiträge zur Philosophie.