Emmanuel Levinas was in France in 1930 and reveals that, even at this early stage, he enlisted in the French army. In 1940 he was captured and spent the remaining five years of the war in two prisoner-of-war camps. Upon being liberated he returns to Lithuania and finds-out that his parents and siblings had been killed by the Nazis, while his wife, whom he had left behind in Paris, had survived thanks to the help of French nuns who hid her. Levinas eventually became one of the greatest ethical philosophers of the 20th century.
In one of his books, Levinas writes a special dedication that reads: “To the memory of those who were closest among the six million assassinated by the National Socialists, and of the millions of all nations, victims of the same hatred of the other man, the same anti-Semitism” 
According to Levinas, whenever a human face calls out to me. I can only respond with the words, “Here I am ….” We might wonder: “Why should I feel responsible in the presence of another person’s face?” But that is precisely why Cain asks of God: “Am I my brother’s keeper?” Cain was not being sarcastic or coy with his question to God. Quite the contrary: Cain’s question reveals to us that he is a man who has yet to learn and appreciate the importance of human solidarity. Cain feels as though each person lives solely for oneself and that everything is permitted. He has no idea what it means to be responsible for another human being.
Although Cain’s answer is sincere, his question reveals that he lacks a conscience; he is out of touch with his own humanity. He doesn’t understand that the human face is special because it bears a trace of God in each person. Yet, God holds Cain accountable—not because of any verbal commandments instructing how not to behave toward his brother. Levinas writes, “The human face is different speaks out and speaks to me without words, ‘Look at me, I am a human being much like yourself. Respect me as you would want to be respected.’”
Even without hearing a divine commandment, “Thou shall not kill,” certain truths are embedded within the soul. Whenever we see a human face suffering, we ought to perceive the Word of God telling us, “You shall not kill” and respond with the gift of presence, “Here I am …. how can I help?”
 OB, vii.