Life can be likened to the transit of the sun across the sky. The moment the sun pokes its head above the horizon; birth. The sun’s climb to its highest point; growth. The sun’s fall back towards the Earth; decay. And the sun’s setting, the instance of its disappearance from our sight? Death.
Birth. Growth. Decay. Death. These two processes and these two events are the banners under which all aspects of life, of existence, fall. The only thing which exists outside of them is non-existence. In our metaphor, non-existence is the absence of the sun, of light. It is darkness. It is night.