A. D. Nock illustrated the problematic nature of the source materials documenting the cult of Mithras by means of the following analogy (Nock 1964: 58): imagine the situation of scholars of twentieth-century Christianity who had the following materials at their disposal: the plans and designs of a few churches, often with bare and undecorated walls; a few altars and paintings; some fragments of glass windows; a few lists of baptized congregation members; and more than seven hundred images of a person affixed to a cross. There would be major problems in reconstructing Christianity from such fragments, as indeed it is difficult to understand Mithraism from similarly scattered remains.

To Nock's analogy I would like to add yet another: Augustine, in one of his tracts (De haeresibus), discusses a total of eighty-eight different Christian “heresies”. Although Mithraism did not operate with a distinction between “orthodox” and “heretical”, the analogy suggests that we recognize a plurality of diverse developments also within this religion.

The cult of Mithras originated in either Rome or Ostia. Although there is evidence in favour of the idea that a specific person created the cult, an “unknown religious genius” to quote M. P. Nilsson (1974: 675), there is no agreement on the validity of such a hypothesis. Mithraism clearly combines innovative elements with existing traditions: it contains elements familiar from Oriental Hellenistic mystery cults, references to an astrological cosmology and a number of Iranian names and terms, including key concepts such as nama, “salvation”.