Life is like a riddle or a play – it is a mystery, not unlike the mystery plays of Medieval Europe. Brahman /reality/God manifests the whole of its grandeur, splendor, and beauty, and Life is that manifestation, an unimaginable and superb spectacle. But there are obvious limitations in it from the perspective of a being such as man (a self-reflecting, limited being): there are the undeniable facts of death and decay, as the young Buddha contemplated in front of him when he left his palace, and that needs an explanation since man’s capacities are also obviously limited.
These are the facts of existence, and it is useless to ask the Supreme Being and originator of life on earth why He did not create existence without death and decay being it’s inevitable and unwelcome companions. So man has to learn and accept that there cannot be growth and reproduction – no life – without there also being the dissolution of forms. This is the play of opposites inherent in all life, primarily the pair male-female (yang/yin). This play is not just a metaphor, but a reality. Without this play – which is manifestation itself – there would not be life and its disclosure and endless development and reproduction.
Man then learns that there cannot be unity without multiplicity, not one without two… and that he is, in his most intimate being or essence, that Unity. It is in Oneness that reality, completion, and intelligibility – and beauty – resides. God/Brahman did not make a mistake or willingly produced something deficient, incomplete.