Dasein's intentional openness to the complicated presence of beings with regard to a unitary temporal horizon (praesens). In the turn, this outcome is reconsidered from a complemented perspective, i.e., in terms of the complicated unity of being₃ as the structural correlation that makes possible the reciprocity of being₂ and Dasein. The turn is thus the move from

• the metaphysical attempt to ground the immediate relationship between being₁ (givenness of presence) and thinking (receptivity to presence) in either the absolutely simple unity of being₁ (Parmenides) or the absolutely simple unity of thinking (Kant) to
• the postmetaphysical experience of the complicated and differential unity of presence and nonpresence in an event of reciprocal correlation (Ereignis or being₃) between being₂ and thinking.

The Emergence of the Fourfold:
Complicated Presence as Intimate Unity

Introduction to Metaphysics (1935): The Four Differentiations of Presence

At the end of the 1935 course Introduction to Metaphysics, Heidegger explicitly announces the turn that his approach has taken. The question concerning human being is now determined exclusively in terms of the question concerning being; from this perspective, the essence of the human being is to be conceived as the site (Stätte) required for the opening up (Eröffnung) of being, and as the open “there” (Da) in which beings are constituted and “come to work (Werk),” i.e., find their proper meaningful functions (EM, 156/IM, 219). The greatest part of this important course consists of a historical reflection on four central ways of differentiating and delimiting being from different senses of un-being or non-being in ancient and modern philosophy (EM, 154/IM, 216):

1. being and becoming (Werden; i.e., “is” and “is coming to be”): being as permanence, as opposed to change;
2. being and appearance (Schein; i.e., “is” and “seems to be”): being as the ideally self-identical essence or prototype, the Parmenidean pure presence or the Platonic idea, as opposed to the multiple manifestations or instantiations that “emulate” the paradigmatic model;

Jussi Backman - Complicated Presence: Heidegger and the Postmetaphysical Unity of Being