Commentary on Heidegger's Being and Time: Dasein pp. 32-5, 67-77

Dasein is the special name Heidegger designates for human being. He uses this word for two reasons. One, it estranges us from other concepts designating the human being, concepts about which we already have assumptions and which if Heidegger uses there will be several risks for misunderstanding. But a second reason Heidegger uses the concept is because of the wordplay of the German Da and Sein, in conjunction literally "being there." Heidegger wants to say that something about this wordplay serves as a clue to the basic constitution of our being. We are beings already "there," that is, already situated in a world.

Even though we're using a special term, Heidegger believes we're still at risk of misunderstanding of our nature because of our inherited self-understanding which, in the Western tradition, comes from ancient Greece and medieval Christianity. Folks like Plato formulated an understanding of being and folks like Thomas Aquinas formulated the theological understanding.

We are also at risk, Heidegger believes, of looking to preexisting fields in order to understand the human constitution, but Heidegger says this is no help for the philosophical project. The example he uses is the ethnologist who studies so-called primitive civilizations as a clue toward understanding, say, early humanity and by implication some of the basic characteristics of human nature. Heidegger wants to say this will not get to the philosophical root because a field like ethnology already has built-in assumptions that will cloud the investigation whereas a broader philosophical project, Heidegger thinks, will disabuse of certain of these presuppositions.