Kook wrote as a mystic, in notebooks of aphoristic, poetic Hebrew that his editors, above all his son Zvi Yehuda and his disciple David Cohen, the Nazirite, gathered into books: Orot, Lights, on the holiness latent in national revival; Orot HaTeshuvah, The Lights of Penitence, in which return to God is a cosmic movement rather than a private repair; Orot HaKodesh, the great collection of his contemplative writing. His central conviction was that holiness is not a fenced precinct: the secular, the heretical, even the rebellious carry sparks of the sacred, and the apparent war between faith and modernity is a stage in a larger harmony only teshuvah, return, will complete. Tolerance, in Kook, is a metaphysical position and not a temperament.
His legacy is contested in exactly the way his life was. Religious Zionism built itself on his teaching; after 1967 his son's reading of it, sharpened toward the sanctity of the land, powered the settlement movement, and scholars still argue whether the father's universalist mysticism authorizes the son's territorial politics. The atlas records the doctrine of Religious Zionism as its own entry, with Kook at its head, and the standard English gateway to his writing remains Ben Zion Bokser's Paulist Press translation of the penitence and holiness texts, through which readers far from any of these arguments continue to meet him simply as one of the twentieth century's great mystics.