“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.” 

This quote from Plato frames the entire text. It indicates the central goal of Being and Time—namely, that it aims to problematize our existing, and uncritical, understanding of Being, so that we can come to a deeper understanding of it.

“The term phenomenology expresses a maxim which can be formulated as ‘To the things themselves!’” 

Heidegger, using a slogan from Husserl, gives a provisional definition of phenomenology. It suggests a return to the way things are originally experienced, prior to ossified theoretical assumptions about them. However, the apparent obviousness and simplicity of this statement belies a far more complex and problematic reality that will confront any genuine attempt to “return to the things themselves.”

“[…] it is one thing to give a report in which we tell about entities, but another to grasp entities in their Being. For the latter task we lack not only most of the words but, above all, the ‘grammar.’”

The task of phenomenology is already starting to look more difficult. Ordinary language and grammar contain certain sedimented ontological assumptions relating to the primacy of presence. As such, we cannot straightforwardly rely on ordinary means of expression to develop the ontological problematic.