Levinas argued that ethics, not ontology, is "first philosophy" - the face-to-face encounter with another person confronts the self with an infinite ethical demand that precedes and cannot be reduced to any theoretical account of being. In "Totality and Infinity" (1961) and "Otherwise than Being" (1974) he criticized the Western philosophical tradition from Parmenides to Heidegger for "totalizing" the Other into categories of the Same, erasing the Other's irreducible alterity.
Intellectual setting
Levinas developed his ethics of alterity in direct critical response to his teacher Heidegger's fundamental ontology, particularly after Heidegger's embrace of Nazism, and against the background of the Holocaust, which shaped his insistence that responsibility for the other person cannot be subordinated to any system or totality.
Key ideas
The face of the Other and ethics as first philosophy
Levinas argued that the encounter with another person's "face" issues an ethical command—"thou shalt not kill"—that precedes and cannot be derived from ontology or epistemology, making ethics rather than metaphysics the true starting point of philosophy.
Critique of totality
Levinas argued that Western philosophy has characteristically sought to comprehend the Other by reducing it to categories of the knowing self (the Same), a "totalizing" violence that his philosophy of infinite alterity and responsibility for the Other seeks to interrupt.
Legacy
Levinas became a central figure of postwar continental and Jewish philosophy, decisively influencing Derrida's later ethical turn and shaping subsequent feminist, postcolonial, and care-ethics accounts of responsibility for the Other.