Abstract It is widely recognized that Heidegger's analysis of Dasein outlines a novel dissolution of the epistemological problems of modern philosophy. However it has not been fully appreciated that this analysis presupposes a conception of human beings which radically separates them from all natural, animal life. Focusing on Heidegger's analysis of Mitsein it is argued that this separation prevents Heidegger from achieving a conception of human existence which avoids the distortions of the humanist tradition against which it recoils. Against Heidegger, (...) it is argued that a philosophically satisfactory conception of human existence must be more smoothly naturalistic. (shrink)