In his introduction to Michel de Certeau’s Heterologies: Discourse on the Other (Theory and History of Literature) , Wlad Godzich gives as concise a summary of Levinas as you are likely to find: “Against a notion of the truth as the instrument of a mastery being exercised by the knower over areas of the unknown as he or she brings them within the field of the same, Levinas argues that there is a form of truth that is totally alien to me, that I do not discover within myself, but that calls on me from beyond me, and it requires me to leave the realms of the known and of the same in order to settle in a land that is under its rule.  Here the knower sets out on an adventure of uncertain outcome, and the instruments that he or she brings may well be inappropriate to the tasks that will arise.  Reason will play a role, but it will be a secondary one; it can only come into play once the primary fact of the irruption of the other has been experienced.  And this other is not a threat to be reduced nor an object that I give myself to know in my capacity as a knowing subject, but that which constitutes me as an ethical being: in my originary encounter I discover my responsibility for the existence of this other, a responsibility that will lie at the root of all my subsequent ethical decisions.  Knowledge and its operations are subordinated to this initial ethical moment, for the responsibility that I then experience is the very ground of my response-ability, that is, my capacity to communicate with others and with myself in noncoercive ways.  Reason can now deploy itself in the field that has been opened up by the relation I have to the other.  It is a reason chastised, not likely to seek hegemonic control, for were it to do so it would have to do violence to my self as the self that is in this relation of response-ability to the other.”