David Sessions explains:
While Heidegger’s central argument was that the meaning of Dasein is nothing more than its existence as possibility—the meaning of individual human being is its being “thrown” into a particular temporal situation—Levinas argued that we are constituted by something even more fundamental than where we find ourselves: the mysterious relation with others that begins in language. That relation places a demand upon us, outside history, that we cannot understand nor escape; it is the ground of our ethical responsibility. Heidegger’s notion of being, where Dasein encounters others only on the basis of its own self-understanding, devalues others by making them like objects that we “possess” and “dominate” by forcing them into our conceptions.
via Emmanuel Levinas and the Receding Possibility of the Infinite | Patrol – A review of religion and the modern world.