Holding to the truth of death—death is always most/just [one’s] own—shows another kind of certainty, more primordial than any certainty regarding beings encountered within the world or formal objects;for it is the certainty of being-in-the-world.
Martin Heidegger, Being and Time
NB. A slightly different point is concept of aporia
(inevitable paradoxes) which was described by Derrida as significant in semantics because all assertions of "what is" rely in part for their meaning on differentiation from "what is not". In that sense we cannot contextually appreciate
the word "life" except with respect to the word "death".