Lévinas' phenomenological account of the "face-to-face" encounter serves as the basis for his ethics and the rest of his philosophy. For Lévinas, "Ethics is first philosophy." Lévinas argues that the encounter of the Other through the face reveals a certain poverty which forbids a reduction to Sameness and, simultaneously, installs a responsibility for the Other in the Self.
The major difference between Buber's account of the I and Thou relation and the ethics of the face-to-face encounter is the application of Lévinas' asymmetry towards the other. For Buber, ethical relation meant a "symmetrical co-presence," while Lévinas, on the other hand, considers the relation with the other as something inherently asymmetrical: the other as they appear, the face, gives itself priority to the self, its first demand even before I react to it, love it or kill it, is: "thou shalt not kill me". Such a demand for Lévinas is prior to any reaction or any assertion of freedom by a subject. The face of the other in this sense looms above the other person and traces "where God passes." God (the infinite Other) here refers to the God of which one cannot refuse belief in Its history, that is the God who appears in traditional belief and of scripture and not some conceptual God of philosophy or ontotheology.
In the face-to-face encounter we also see how Levinas splits ethics from morality. Ethics marks the primary situation of the face-to-face whereas morality comes later, as some kind of, agreed upon or otherwise, set of rules that emerge from the social situation, wherein there are more than just the two people of the face-to-face encounter.