From Totality and Infinity:

For the presence before a face, my orientation toward the Other, can lose the avidity proper to the gaze only by turning into generosity, incapable of approaching the other with empty hands. This relationship established over the things henceforth possibly common, that is, susceptible of being said, is the relationship of conversation. The way in which the other presents himself, exceeding the idea of the other in me, we here name face. This mode does not consist in figuring as a theme under my gaze, in spreading itself forth as a set of qualities forming an image. The face of the Other at each moment destroys and overflows the plastic image it leaves me, the idea existing to my own measure and to the measure of its ideatum–the adequate idea. It does not manifest itself by these qualities, but καθ᾿ αὑτὸ. It expresses itself. The face brings a notion of truth which, in contradistinction to contemporary ontology, is not the disclosure of an impersonal Neuter, but expression: the existent breaks through all the envelopings and generalities of Being to spread out in its “form” the totality of its “content,” finally abolishing the distinction between form and content. This is not achieved by some sort of modification of the knowledge that thematizes, but precisely by “thematization” turning into conversation. The condition for theoretical truth and error is the word of the other, his expression, which every lie already presupposes. But the first content of expression is the expression itself. To approach the Other in conversation is to welcome his expression, in which at each instant he overflows the idea a thought would carry away from it. It is therefore to receive from the Other beyond the capacity of the I, which means exactly: to have the idea of infinity. But this also means: to be taught. The relation with the Other, or Conversation, is a non-allergic relation, an ethical relation; but inasmuch as it is welcomed this conversation is a teaching [enseignementJ. Teaching is not reducible to maieutics; it comes from the exterior and brings me more than I contain. In its non-violent transitivity the very epiphany of the face is produced. The Aristotelian analysis of the intellect, which discovers the agent intellect coming in by the gates, absolutely exterior, and yet constituting, nowise compromising, the sovereign activity of reason, already substitutes for maieutics a transitive action of the master, since reason, without abdicating, is found to be in a position to receive. (TI 50-51)