Being and Time begins with a quote from Plato: “For manifestly you have long been aware of what you mean when you use the expression ‘being’. We, however, who used to think we understood it, have now become perplexed” (19). With this quote, Heidegger lays the grounds not only for what will follow in his Introduction, but for the direction and purpose of this work as a whole. That is, he seeks to re-awaken an interest in the question and meaning of “Being,” something that has become so taken for granted, and familiar, in philosophy and life that we have forgotten it is an issue. It is, provisionally stated, the question of the unifying meaning and structure underpinning all specific entities, or “beings,” that exist. It is the central philosophical question of how anything is possible at all.

Heidegger goes on to deal with some potential objections to this basic project. These are that we already understand Being whenever we use any concept, that it is “self-evident,” and, oppositely, that as a universal concept, it is obscure and indefinable. Firstly, though, the fact that something is used does not necessarily mean we understand it. Second, the alleged obscurity of the concept is all the more reason why it needs clarification.