Henry Corbin, Alone with the Alone:
At this point we must recapitulate the distinction, fundamental for us, between allegory and symbol; allegory is a rational operation, implying no transition either to a new plane of being or to a new depth of consciousness; it is a figuration, at an identical level of consciousness, of what might very well be known in a different way. The symbol announces a plane of consciousness distinct from that of rational evidence; it is the “cipher” of a mystery, the only means of saying something that cannot be apprehended in any other way; a symbol is never “explained” once and for all, but must be deciphered over and over again, just as a musical score is never deciphered once and for all, but calls for ever new execution.