Once, when Rabbi Zalman Schachter-Shalomi was still a young Hillel director, he took his students to meet the seventh Lubavitcher Rebbe, Rabbi Menachem Mendel Schneerson (1902-1994). To his embarrassment, one of his students asked the Rebbe, "What is a rebbe good for?" But the Rebbe was not offended and offered this amazing response: "I can't speak about myself; but I can tell you about my own rebbe. For me, my rebbe was the geologist of the soul...