Heidegger uses the word “Dasein” to refer to what customarily might be called the self or “I”; or, as he more cautiously puts it, to “this entity which each of us is himself” (BT 27). But while the denotations of the words “self” and “Dasein” may be the same, the connotations differ radically. When properly understood, “Dasein” captures the unique being of the “I am”, one that gets misconstrued by such terms, for example, as “self”, “ego”, “soul”, “subjectivity” or “person”. For Heidegger, what constitutes the very “am” of the “I am” is that being is an issue for it: is a question and a matter about which it cares. This entity that I am understands this implicitly. More radically, it is this understanding, or the place where this understanding of being occurs. Hence “Dasein” means the self as the there (Da) of being (Sein), the place where an understanding of being erupts into being.

“Being-in-the-world” is Heidegger's descriptive interpretation of the self as Dasein. For Heidegger, as we shall come to see, description and interpretation need not be at odds. One sort of interpretation (Auslegung), as a laying-out of that which is only tacit, is description. “Being-in-the-world” is intended to capture descriptively various dimensions of what it means for Dasein “to be”. But much more needs to be said, in the way of interpretation, about this description.