The enlightenment (Bodhi) of the Buddha was simultaneously his liberation from suffering and his insight into the nature of reality. The widely accepted doctrine of dependent origination states that any phenomenon ‘exists’ only because of the ‘existence’ of other phenomena in a complex web of cause and effect. For sentient beings, this amounts to a never-ending cycle of rebirth (samskra) according to the law of karma (Pali: kamma) and vipāka. Because all things are thus conditioned and transient (anitya, Pali anicca), they have no real, independent identity (anatman, Pali anatta) and so do not truly ‘exist’, although to ordinary minds they do appear to exist. All phenomena are thus fundamentally insubstantial and empty. Wise human beings, who possess "insight into the knowledge of how things are", renounce attachment and clinging which cause suffering (dukkha, Pali dukkha), transform the energy of desire into awareness and understanding, and eventually attain nirvana.