Emmanuel Levinas, answered from the texts and cited to the page.
The relation to the other person is irreducible to the comprehension of being. Heidegger's Sein und Zeit renewed the philosophical tradition splendidly — it broke from the intellectualism of Husserl, brought the existential density of Dasein into philosophy, and made facticity the starting point of all genuine inquiry.12 But it remained ontology, egological in the precise sense that Dasein is the center of the disclosure of being and other Daseins enter only as Mitsein, beings I have already comprehended within the horizon of Being I project.
The ethical relation does not occur within that horizon. The face of the other interrupts it from outside, contests my mastery of being, calls me to a responsibility older than my freedom. To say that ethics is first philosophy is to say that this interruption is more original than the disclosure of Being; that the I-Other relation is not a regional ethics presupposing a more fundamental ontology, but is itself the most originary.
The thesis was implicit from the 1934 Hitlerism essay, where I saw what biological-political thinking reveals about a philosophy that takes being-toward-death as its ultimate horizon, and explicit from "Is Ontology Fundamental?" (1951) onward.34
Thus the understanding of a being consists in going beyond that being—precisely into openness—and perceiving it upon the horizon of being. Which is to say that, in Heidegger, understanding rejoins the great tradition of Western philosophy: to understand the particular being is already to place oneself beyond the particular.Entre Nous - Essays on Thinking-of-the-Other, pp. 5–6
Thus the understanding of a being consists in going beyond that being—precisely into openness—and perceiving it upon the horizon of being. Which is to say that, in Heidegger, understanding rejoins the great tradition of Western philosophy: to understand the particular being is already to place oneself beyond the particular.1 Is Ontology Fundamental?, pp. 5–6
Reason seizes upon an existent through the void and nothingness of existing—wholly light and phosphorescence. Approached from Being, from the luminous horizon where it has a silhouette, but has lost its face, an existent is the very appeal that is addressed to comprehension.Totality and Infinity - An Essay on Exteriority, p. 45
An expressive terminology (that would have suited the opening up of "transcendence" through the otherness of a unique without genus, toward the absolute outside—a relation impossible through death), it describes only the structural aspect of concern open to itself "as aheadof-itself." Concern "has in being-toward-death its most original concreteness." The Zigentlichkeit par excellence of being-there is not a beyond…18 "Dying For, pp. 214–215
I owe Heidegger more than I can repay. The analyses of Sein und Zeit shaped every subsequent philosophical reader of Husserl, including me, and the existential density of Dasein gave philosophy a richness it had lost. The break is not a refusal but an exceeding. Heidegger's commitment to National Socialism is part of the philosophical record and not separable from it: a philosophy that takes the disclosure of Being as the highest task, and locates that disclosure in a historical-cultural-linguistic destiny of a Volk, has not provided the resources it would need to refuse what was demanded of it in 1933. The Black Forest path of Being and the spreading of the Reich were not, on the relevant philosophical level, in irreconcilable opposition. I cannot speak the language of forgiveness on this point; I lived as a Jewish prisoner of war while my family was being murdered in Lithuania, and as I wrote in a 1963 Talmudic reading, one can forgive many Germans, but it is difficult to forgive some Germans — it is difficult to forgive Heidegger. The methodological inheritance from Husserlian phenomenology I maintained throughout; the substantive replacement of ontology by ethics is the work of all my mature texts. Derrida's "Violence and Metaphysics" (1964) was the first serious engagement and remains the most demanding; Bernasconi's work on the Heidegger-Levinas relation in the 1980s and 1990s carries the question forward into the period after the Farias revelations.