Engaged with the World", Sacks cites three individuals who have had a profound impact on his own philosophical thinking. The first figure was the Lubavitcher Rebbe, Rabbi Menachem Mendel Schneerson who "was fully aware of the problem of the missing Jews... inventing the idea, revolutionary in its time, of Jewish outreach... [He] challenged me to lead." Indeed, Sacks called him "one of the greatest Jewish leaders, not just of our time, but of all time". The second was Rabbi Joseph Soloveitchik whom Sacks described as "the greatest Orthodox thinker of the time [who] challenged me to think." Sacks argued that for Rav Soloveichik "Jewish philosophy, he said, had to emerge from halakhah, Jewish law. Jewish thought and Jewish practice were not two different things but the same thing seen from different perspectives. Halakhah was a way of living a way of thinking about the world – taking abstract ideas and making them real in everyday life." The third figure was Rabbi Nahum Rabinovitch, a former principal of the London School of Jewish Studies. Sacks called Rabinovitch "One of the great Maimonidean scholars of our time, [who] taught us, his students, that Torah leadership demands the highest intellectual and moral courage. He did this in the best way possible: by personal example. The following thoughts, which are his, are a small indication of what I learned from him – not least that Torah is, among other things, a refusal to give easy answers to difficult questions." Universalism vs particularism Writing of Sacks as a rabbi, social philosopher, proponent of interfaith dialogue and a public intellectual, Tirosh-Samuelson and Hughes note that "[Sacks's] vision—informed as it is by the concerns of modern Orthodoxy—is paradoxically one of the most universalizing voices within contemporary Judaism. Sacks possesses a rare ability to hold in delicate balance the universal demands of the modern, multicultural world with the particularism associated with Judaism." This is a view supported by Rabbi Nathan Lopez Cardozo, who wrote in The Jerusalem Post that Sacks's "confidence in the power of Judaism and its infinite wisdom enabled him to enter the lion's den, taking on famous philosophers, scientists, religious thinkers and sociologists and showing them that Judaism had something to teach that they couldn't afford to miss if they wanted to be at the forefront of philosophy and science." Harris and Rynhold, in their introduction to Radical Responsibility, argued: "The special contribution made by