What do you think Elie Wiesel meant when he said that he and some of his friends believed that "the memory of evil will serve as a shield against evil; that the memory of death will serve as a shield against death"?

This is a part from Elie Wiesel's Nobel lecture and he is talking about the memory of the Holocaust and the Second World War as Wiesel was a survivor of the Holocaust and the Nazi prosecution. He believes that the past will serve as reminder and a shield so the horrors he and others went through would never repeat.