Rabbi Abraham Isaac Kook (1865-1935) was the first Ashkenazic chief rabbi of mandatory Palestine. Admired for the incredible diversity of his talents and interests--talmudist, halakhist, kabbalist, mystic, theologian, moralist, poet, and communal leader--Rav Kook's world outlook extolled breadth and derided narrow specialization. More than any other Orthodox thinker in modern times, he addressed, squarely and boldly, the confrontation between Judaism and the modern world. Kook serves as a natural model to those Jews who seek a religious understanding of and response to the culture and politics of the modern age. These essays, most published here for the first time, offer a range of analyses and interpretations covering, in an accessible, systematic, and comprehensive fashion the major areas of Rav Kook's thought. Among the issues discussed are: his relationship to the Jewish mystical, philosophical, and halakhic traditions; poetry and spirituality; harmonism and pluralism; tolerance and its limits; Zionism, messianism, and politics; and Rav Kook today.