In this paper I outline Hans Jonas’s thesis of the “existential” character of biological life and compare it with statements made by the early Heidegger concerning the essential enworldedness of all living beings. I then critically examine this thesis in the light of Heidegger’s own later refutation of his views and consequent reversal of his former position on life. I argue that while both thinkers are correct to attribute a radical openness to organic life as such, Heidegger is correct is (...) restricting the existential dimension to specifically human life given certain logical constraints built into the concept of existence itself. (shrink)