In 1905, a young German rabbi, Léo Baeck, published The Essence of Judaism, a book that made him a famous proponent of the Jewish people and their faith. Over time he became a spiritual leader of the European Jews, the leader of a Jewish liberal movement in both Europe and the United States, and one of the most influential Jewish thinkers worldwide. His faith and teachings as a rabbi, from within the concentration camps and after, helped fuel a renaissance in European Judaism after the horrors of the Holocaust. In this detailed biography, Maurice-Ruben Hayoun tells not only the story of the man, but also the story of his place in the long pathway of Judaism, from traditional beginnings to the tragedy of the twentieth century.

Maurice-Ruben Hayoun introduces Léo Baeck in comparison to his predecessors—including Moise Mendelssohn—emphasizing Baeck's role in Jewish history. Hayoun notes that although the classical tradition was essential to Baeck, he also promoted Jewish integration into the European culture. Indeed, Baeck was passionate about culture in general and strongly believed in the possibility of tolerance for and by all peoples.

Baeck's childhood was spent in Lissa—then part of Germany, now of Poland—and he was heavily influenced by his father's role as a rabbi. He decided to follow in his father's footsteps but chose to study for the rabbinate in Berlin in a much more liberal environment. During his time in Berlin, he witnessed Kaiser Wilhelm II's abdication and the establishment of the Weimar Republic. He then watched as anti-Semitism started to grow in Germany and as Hitler's National Socialist politics increased in power.

Baeck stayed in Germany, despite being offered help in leaving from influential people in many Western countries, believing he could help best from the midst of the German state. He would stay faithful to his people until the end, refusing to leave Germany as long as there were still Jewish people who needed help. When he was deported in 1943 to the concentration camp at Therensienstadt, he started a spiritual resistance, teaching Torah to the inmates. Hayoun paints the portrait of a brave leader, a wise thinker, who never gave up on renewal and reconstruction built on dialogue and open-mindedness.