"I will not try to do justice here to the richness of Heidegger's constructive account of what he calls the 'phenomenological chronology of being.' What is of fundamental importance in it for the purposes of this discussion is the notion that being cannot be identified with the 'is' of the present tense, no matter how disguised, or with the mode of presence that corresponds to it. Instead, being is complexly articulated in the way that the system of tenses expresses, and there is no possibility of simplifying this complex ordering in favor of a single one of its modalities. The analysis of this articulation of being into its various modalities is ontology; and perhaps the most radical claim that Heidegger makes is that ontology has an essentially temporal character. This is because the distinctions it explicates among the modalities of being — between the 'is' and the 'is not' and between 'is possible' and 'not possibly' — have to be understood in temporal terms. The articulated structures of being are thus inextricably bound up with the distinctions of past, present, and future that are comprised in our own temporality as this was characterized in Being and Time. What 'is,' is thus necessarily what will or will not be. But these temporal qualifications of the articulations of being also articulate presence, which is, therefore, not just a matter of the static immediacy of the present tense. To put this point in a maximally paradoxical way, presence also compromises absence. It takes the form of the 'has been' and the 'will be' as well as of the 'is,' and the being of the entities that form part of the world of Dasein is understood in just this ecstatic mode that characterizes the temporality of Dasein. In psychological terms, we would speak here of 'memory' and 'expectation,' but it is just this psychological mode of description that Heidegger avoids because it obscures what most needs attention for the purposes of ontology. Instead, he speaks of the presence of such entities as their presence-to the entity — Dasein — which is itself temporal in the way that makes this presence possible. This presence is also declared to be the being of those entities, once it is accepted that the concept of being is complexly articulated in the manner that has been described and that corresponds to the set of temporal distinctions that Dasein itself deploys" (Guignon 1993:103-104).
Guignon, Charles, ed.
1993 The Cambridge Companion to Heidegger. Cambridge: Cambridge University Press
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