Full Idea
Dasein is an entity which, in its very being, comports itself understandingly towards that being. ...Mineness belongs to an existent Dasein, and belongs to it as the condition which makes authenticity and inauthenticity possible.
Gist of Idea
Dasein is being which can understand itself, and possess itself in a way allowing authenticity
Source
Martin Heidegger (Being and Time [1927], p.78), quoted by Mark Wrathall - Heidegger: how to read 1
Book Reference
Wrathall,Mark: 'Heidegger: how to read' [Granta 2005], p.6
A Reaction
He might eventually persuade me that Dasein is so different from mere material being that it deserves a category of its own. But a reductive account of mind is also a reductive account of being.