 Nevertheless, Heidegger and Nietzsche are both important sources for postmodernism's critical de-structuring or displacement of the signature concept of modern philosophy, the “subject,” which is generally understood as consciousness, or its identity, ground, or unity, and designated as the “I.” Where Nietzsche finds in this concept the original metaphysical error produced by morality and the communicative needs of the herd, Heidegger sees in it the end and exhaustion of the metaphysical tradition, inaugurated by the Greeks, in which being is interpreted as presence.  Here, being is the underlying ground of the being of beings, the subiectum that is enacted in modern philosophy as the subject of consciousness.  But in Being and Time Heidegger conceives the human being as Dasein, which is not simply a present consciousness, but an event of ecstatic temporality that is open to a past (Gewesensein) that was never present (its already being-there) and a future (Zu-kunft) that is always yet to come (the possibility of death).  The finitude of Dasein therefore cannot be contained within the limits of consciousness, nor within the limits of the subject, whether it is conceived substantively or formally.