'Very definition' is a bit of a flowery twiddle, but Heidegger did see it as essential (in a non-Platonic sense) to Dasein that it take a stand on its own being. That's what we do, and hammers and stones and insects don't.May be I have this wrong, but isn't that a bit deterministic as the 'very definition'? I can see how that gets to the cul-de-sac of post-modern identity politics (or the worst of it).