Though historians have given up trying to outline a rigid definition to categorize all mystery cults, a number of characteristics that the mystery cults shared can be outlined. All the mystery cults placed emphasis on the secrecy of their practices and an emotional initiation ritual for a new member to join the group. The members were voluntary participants, had nocturnal settings and preliminary purifications for their gatherings, there was an obligation to pay in order to participate, promised rewards for this life and the next, and the older mysteries were located at a variable distance from the nearest city. Furthermore, they were all, with the exception of the Mithraic cult, open to all people, including men and women, slaves and freeman, the young and old, etc. However, the expenses required to participate in all the rituals often precluded many from joining. And though the mysteries were secret, they were not very mysterious.