A mystery religion was a certain type of cult or religion that proliferated during the Hellenistic era. The many mystery religions promised eternal life to carefully-selected initiates who, following much preparation, had been deemed worthy to receive the secret knowledge guarded by the particular mystery they had joined. The various mystery religions typically did not seek to convert people from all walks of life but appealed instead to special groups, for instance, women, soldiers, or intellectuals. The knowledge in question frequently involved Eastern deities or philosophy.
During the first centuries of the Christian era, the Christian church sought to distinguish itself from the mystery religions with which it was often confused. In fact, Christianity was quite unlike the many mystery religions in its fundamentals. It disseminated its beliefs openly, appealed to both sexes, to all nations, and to people from both high and low social strata. Perhaps most critically, the Christian Church taught that eternal life is a free gift of God that is obtained by faith and a resultant lifestyle change, not earned through the acquisition of knowledge.