Tsimtsum (contraction) and hitpashtut (expansion). These two kabbalistic terms aptly describe the thought of Bezalel Naor. Though diametrically opposed, they come together in this unique moment. The author is at once a "hedgehog" and a "fox," in the usage of Isaiah Berlin. Naor brings to the table both the intense focus, the razor-sharp analysis of Rav Soloveitchik of Boston, and the synthetic, unitive perception of reality, of Rav Kook (whose bon mot was "kelaliyut," "universality"). This dialectic thought, constantly "zooming" in and out, forever shifting gears from "micro" to "macro," is unleashed on the entire process of Judaism: Torah, Talmud, the challenge of Christianity and Islam, Maimonides, Kabbalah, Hasidism, Messianism, and the specialty of the house-Rav Kook. The final section of Book Reviews includes a wide array: Kozhnitser Maggid, Kafka, Paul Celan, Leonard Cohen, Yehudah Don Yahya, Meshulam Rath, and Rabbi Nahman of Breslov. The reader is invited to embark on this enchanted intellectual and spiritual journey, as the author attempts "navigating worlds." (One of the chapters of the book is entitled "Rav Kook's Space Odyssey.")