[The[concept of Emptiness or Void (shunyata) which is so central to the whole Mahayana system of belief.
The concept, often described in English as "nondualism", is extremely hard for the mind to grasp or visualize, sine the mind engages constantly in the making of distinctions and nondualism represents the rejection or transcendence of all distinctions. The world perceived through the senses, the phenomenal world as we know it, was described by early Buddhism as empty because it was thought that all such phenomena arise from causes and conditions, are in a constant state of flux, and are destined to change and pass away in time. They are also held to be "empty", in the sense that they have no inherent or permanent characteristics by which they can be described, changing as they do from instant to instant. But in Mahayana thought it became customary to emphasise not the negative but rather the positive aspects of or imports of Emptiness.If all phenomena are characterised by a quality of Emptiness, then Emptiness mush constitute the unchanging and abiding nature of existence, and therefore the absolute or unchanging nature world must be synonymous with the phenomenal one. Hence all mental and physical distinctions that we perceive or conceive with our minds must be part of a single underlying unity. It is this concept of Emptiness or nonduality that leads the Mahayana texts to assert that samsara, the ordinary world of suffering and cyclical birth and death, is in the end identical with the world of nirvana, and that earthly desires are enlightenment.