It is convenient to term the Persian and Hellenistic deity Mitra, to distinguish him from the god of the Roman mystery-cult. Mitra was an ancient Indo-European divinity, a member of a pantheon which can be reconstructed by means of evidence from North India and Iran. The earliest document to name the god dates from the second millennium bc: on a fourteenth-century clay tablet from Boghaz-Köy in modern Turkey, the former capital of the Hittite empire, Mitra is invoked as a guarantor of an agreement between the Hittites and a neighbouring people, the Mitanni (V 16). But Mitra is not only the god of treaties, of agreements, he is treaty or contract personified. In Avestan (the eastern dialect of Old Iranian), miθra- means ‘treaty’ or ‘contract’. 15