To Judaism Christians ascribe the glory of having been the first religion to teach a pure monotheism. But monotheism existed long before the Jews attained to it. Zoroaster and his earliest followers were monotheists, dualism being a later development of the Persian theology. The adoption of monotheism by the Jews, which occurred only at a very late period in their history, was not, however, the result of a divine revelation, or even of an intellectual superiority, for the Jews were immeasurably inferior intellectually to the Greeks and Romans, to the Hindus and Egyptians, and to the Assyrians and Babylonians, who are supposed to have retained a belief in polytheism. This monotheism of the Jews has chiefly the result of a religious intolerance never before equaled and never since surpassed, except in the history of Christianity and Mohammedanism, the daughters of Judaism. Jehovistic priests and kings tolerated no rivals of their god and made death the penalty for disloyalty to him. The Jewish nation became monotheistic for the same reason that Spain, in the clutches of the Inquisition, became entirely Christian.