This universe that we are in now, as we have experienced it so far, is a result of combining both the One and contingency, purpose and randomness. Evil happened accidentally as a result of interaction between will and contingency. Accidents were possible in the universe because the universe is not the pure One, it is only a mirror image of it, and that image is not fully exact because it contains contingency, and therefore the One is not all powerful within the realms of the universe. Evil is a momentum in which will is submerged by contingency, loses connection with the Absolute, gets turned inside out, and starts to be used for the opposite purpose of what it is originally meant for. This is why 'evil' spells 'live' backwards.
As part of the exploration process of all posible potentials, the universe was divided into several planes/dimensions (physical, plasma, etheric, astral, etc), each containing various proportions of contingency