The trajective displacement of the Western metaphysical thinking is ontologically connected to the trajective displacement of the being as presence (ousia, dasein).
The identity of the presence, constituted as eidos, assumed in the Cartesian cogito a topology vehiculated to the categories of evidence and certainty, becoming, in this way, vulnerable to the domain of the repetition, incorporated in the metastasized form of representation of the Cartesian eidos present to itself and aware of itself, as relation to itself, in itself.
In the interior of the presence (ousia, dasein), the domain of the presence assured, with Descartes, the representation of itself as available truth, replicable by any rational motion of irreducible self-affection logocentric/phonocentric (Derrida)...
...but a notion of presence depends upon a notion of existence, which, in turn, depends upon a notion of being, which, in turn, depends upon a notion of nothing, all this interconnected with a notion of life/death.
Certainly that the notion of presence continues to be, in Philosophy, an open question, that cannot be resolved from solipsistic criteria.
We, human organisms, animals as any others, think in presence, in existence and in life because we are there with the others, with all the others, upon which we depend as survivors and subsistents: we question ourselves, we wish to know of reasons: what does it mean to state that we are? What does it mean to state that the others are? What does it mean to state that we exist, that we (co)exist? What is life? What is death?
Presence/ousia/dasein is not a matter of egocalculation, but a matter of autopoiesis, a matter of enaction.