In a footnote to the preface to the second edition of his Critique of Pure Reason (1787) Kant remarked that ‘it still remains a scandal to philosophy and to human reason in general that the existence [Dasein] of things outside us … must be accepted on faith, and that if anyone thinks good to doubt their existence, we are unable to counter his doubts by any satisfactory proof' (B XL). In Being and Time (1927) Heidegger remarks, somewhat less famously, that the scandal of philosophy, far from being the continuing absence of philosophically satisfactory proof of the existence of the world outside human subjectivity, is rather the very idea that such proof need be sought at all: ‘If Dasein is understood correctly, it defies such proofs, because, in its being, it already is what subsequent proofs deem necessary to demonstrate for it’ (BT, 205).

In other words, the familiar problems of scepticism about the existence of the external world collapse as soon as the place of human beings in the world is properly identified—an attractive thesis, if Heidegger can substantiate it. We need seek no ‘proofs’; we need only remind ourselves of the facts. We are, from the outset, beings-in-the-world. There is no problem about the relation between subjectivity and the objective world. How we are is revelatory of the world. Heidegger's choice of the ordinary word ‘Dasein’, meaning ‘existence’ as in the Kant quotation, to designate the manner of being enjoyed by creatures like ourselves, is of course arbitrary and idiosyncratic, but his purpose is to exploit the word's etymological structure.