The causes which in the second century A.D. prepared the triumph of Mithra—Heliolatry the natural goal of heathenism—Early history of Mithra in the Vedas and Avestas—He is a moral power from the beginning—His place in the Zoroastrian hierarchy—His relation to Ormuzd—The influence of Babylon on the Persian worship—Mithra identified with the Sun—The astral lore of Babylonia inseparable from Mithraism—Yet Mithra and the Sun are distinct in the later Inscriptions—How Mithra worship was modified in Asia Minor—The influence of Greek mythology, philosophy, and art—The group of the Tauroctonus probably first fashioned by a Pergamene artist—Mithra in literature—Herodotus—Xenophon—The _Thebaid_ of Statius—Plutarch—Lucian may have heard the Mazdean litany—Mithra’s first coming to the West probably in the reign of Tiberius—The earliest inscriptions of Mithraism belong to the Flavian age—At the same time, the worship is established in Pannonia—The earliest temples at Ostia and Rome—The power of Mithra in the capital—The secret of the propaganda—Soldiers were the most effective missionaries of Mithra—Slaves and imperial officials of every degree propagate the Persian faith—Its progress traced around Rome and through various regions of Italy, especially to the north—Mithra’s chapels in the valleys of the Alps and on the roads to the Danube from Aquileia—Along the line of the Danube—His remains abundant in Dacia and Pannonia—Chapels at Aquincum and Carnuntum—The enthusiasm of certain legions—The splendid remains of Mithra worship in Upper Germany in the early part of the second century A.D.—Mithra passes on, through Cologne and Boulogne, to London, Chester, York and the wall of Hadrian—Mithra made least impression on W. Gaul, Spain, and N. Africa—In spite of tolerance and syncretism, Mithraism never ceased to be a Persian cult—The influence of astrology—The share of Babylonia in moulding the worship—Yet Greek mystic influences had a large part in it—The descent and ascent of the soul—Yet, although Mithraism came to be a moral creed, it never ceased to be a cosmic symbolism—The great elemental powers—The daemonology of Mithraism—Its affinity with the later Neo Platonism—The evil effect of belief in planetary influences—The struggle between formal and spiritual ideals of religion—The craving for mediatorial sympathy in the moral life was urgent—Mithra was a mediator both in a cosmic and a moral sense—He stands between Cautes and Cautopates, and between Ormuzd and Ahriman—The legend of Mithra as faintly recovered from the monuments—The _petra genetrix_—The adoration of the shepherds—The fountain gushing at the arrow stroke—The legend of the mystic bull—Its chase and slaughter—Its death as the source of resurgent life—The mysterious reconciliation of Mithra and the Sun—Their solemn agape—Various interpretations of the legend—Yet there was a real spiritual meaning under it all—A religion of strenuous combat—How it touched the