As soon as man was capable of conceiving the idea of sin, he had recourse to psychic concealment – or, to put it in analytical language, repressions arose. Anything that is concealed is a secret. The maintenance of secrets acts like a psychic poison which alienates their possessor from the community. In small doses, this poison may actually be a priceless remedy, even an essential preliminary to the differentiation of the individual. This is so much the case that, even on a primitive level, man has felt an irresistible need to invent secrets; their possession saves him from dissolving in the unconsciousness of mere community life, and thus from a fatal psychic injury. As is well known, the many ancient mystery cults with their secret rituals served this instinct for differentiation. Even the Christian sacraments were looked upon as mysteries in the early Church, and, as in the case of baptism, were celebrated in private apartments and only referred to under veil of allegory.

C G Jung