This article begins with Gedankenexperiment proposed in The Adventure of Difference by Gianni Vattimo: Following his suggestion to read Heidegger's fundamental ontology in terms of Nietzsche's The Birth of the Tragedy, we attempt to reinterpret the distinction of the authentic and inauthentic existence in the light of the difference between the Dionysian and Apollonian element, which brings us also to a new view on the existential finitude, individuality and co-existence with others. In the background of these existential features we discover the notion of event that breaks the ecstatic unity of temporality and marks the hermeneutical continuity of existence by the radical discontinuity. The image of existence exposed to the power of event is further elaborated with the help of Henri Maldiney who has introduced into the frame of the fundamental ontology the concepts of trans-possibility and trans-passibility that express the existential openness to the event. Such a reformulation of the fundamental ontology, however, brings us into the sphere of heteronomous thought that, instead of preserving its essential autonomy, unity and integrity, becomes other in its relation to the otherness that is encountered in the event.