[P]hilosophy as the thinking of be-ing is distinct from the thinking of the 'ontological difference.' When Heidegger, already in Being and Time, introduces the notion of ontological difference, he means to think being over against beings. But, as he says in Contributions, this thinking is still bound or de-fined by beings. Thinking the ontological difference is thinking beings and being in their difference. Proceeding from what is present/extant (beings), thinking moves toward being in its difference from beings. One might say that the 'necessity of thinking' called for thinking to say the question of being as ontological difference - but then, drawn on by that very necessity, to think be-ing itself, where be-ing does not get it determination from being-as-other-than-beings, but from be-ing as such.Continued.
Heidegger calls what is present das Anwesende (beings in their presence) and the being of those beings das Anwesenheit (being as what 'grants' beings or what is present). It is possible to translate Anwesenheit as 'presence.' That translation would imply a certain static presence, maybe even a unity - a metaphysical unity. Thus one might be tempted to say that, whereas Heidegger says that his thinking moves out from within a metaphysics of presence or unity, this word here indicates that his thinking remains (imprisoned?) within that metaphysics of presence. But things are not so simple.
In a little text from a larger work entitled 'Die Seinsfrage: Der Holzweg' Heidegger says that all talk of 'being' in Being and Time is thought as Anwesenheit. 'Even the being in "Da-sein" is ecstatic, a manifold emerging to...what emerges [Anwesen zu...Anwesendem].' Then he say, 'Anwesenheit is never and in no way something present [ein Anwesendes]; in this regard it is the nothing.' Hardly a metaphysics of presence! Thus granting a certain unclarity on the level of 'grammar' or literal meanings, the saying/showing in the word Anwesenheit cannot be said adequately in English as 'presence.' So, Anwesenheit as 'presence' becomes Anwesenheit as 'emergence.'
Pp. 25-6