Punabbhava / Punarbhava / rebirth / some people call it reincarnation
Rebirth in Buddhism is the doctrine that the evolving consciousness (Pali: samvattanika-viññana) or stream of consciousness (Pali: viññana-sotam, Sanskrit: vijñāna-srotām, vijñāna-santāna, or citta-santāna) upon death (or "the dissolution of the aggregates" (P. khandhas, S. skandhas)), becomes one of the contributing causes for the arising of a new aggregation. The consciousness in the new person is neither identical to nor entirely different from that in the deceased but the two form a causal continuum or stream.
In traditional Buddhist cosmology these lives can be in any of a large number of states of being including the human, any kind of animal and several types of supernatural being (see Six realms). Rebirth is conditioned by the karmas (actions of body, speech and mind) of previous lives; good karmas will yield a happier rebirth, bad karmas will produce one which is more unhappy. The basic cause for this is the abiding of consciousness in ignorance (Pali: avijja, Sanskrit: avidya): when ignorance is uprooted, rebirth ceases. One of the analogies used to describe what happens then is that of a ray of light that never lands.
There is no word corresponding exactly to the English terms "rebirth", "metempsychosis", "transmigration" or "reincarnation" in the traditional Buddhist languages of Pāli and Sanskrit: the entire process of change from one life to the next is called punarbhava (Sanskrit) or punabbhava (Pāli), literally "becoming again", or more briefly bhava, "becoming", while the state one is born into, the individual process of being born or coming into the world in any way, is referred to simply as "birth" (jāti). The entire universal process that gives rise to this is called saṃsāra.
Within one life and across multiple lives, the empirical, changing self not only objectively affects its surrounding external world, but also generates (consciously and unconsciously) its own subjective image of this world, which it then lives in as 'reality'. It lives in a world of its own making in various ways. It "tunes in" to a particular level of consciousness (by meditation or the rebirth it attains through its karma) which has a particular range of objects - a world - available to it. It furthermore selectively notices from among such objects, and then processes what has been sensed to form a distorted interpretive model of reality: a model in which the 'I am' conceit is a crucial reference point. When nibbana is experienced, though, all such models are transcended: the world stops 'in this fathom-long carcase'.
The Buddha lived at a time of great philosophical creativity in India when many conceptions of the nature of life and death were proposed. Some were materialist, holding that there was no existence that the self is annihilated upon death. Others believed in a form of cyclic existence, where a being is born, lives, dies and then is re-born, but in the context of a type of determinism or fatalism in which karma played no role. Others were "eternalists", postulating an eternally existent self or soul comparable to that in Christianity: the ātman survives death and reincarnates as another living being, based on its karmic inheritance. This is the idea that has become dominant (with certain modifications) in modern Hinduism.
The Buddha's concept was distinct, consistent with the common notion of a sequence of lives over a very long time but constrained by two core concepts: that there is no irreducible self tying these lives together (anattā) and that all compounded things are subject to dissolution, including all the components of the human person and personality (anicca). The story of the Buddha's life presented in the early texts does not allude to the idea of rebirth prior to his enlightenment, leading some to suggest that he discovered it for himself. The Buddha's detailed conception of the connections between action (karma), rebirth and causality is set out in the twelve links of dependent origination.
There are many references to rebirth in the early Buddhist scriptures. These are some of the more important; Mahakammavibhanga Sutta (Majjhima Nikaya 136); Upali Sutta (Majjhima Nikaya 56); Kukkuravatika Sutta (Majjhima Nikaya 57); Moliyasivaka Sutta (Samyutta Nikaya 36.21); Sankha Sutta (Samyutta Nikaya 42.8).
Some English-speaking Buddhists prefer the term "rebirth" or "re-becoming" (Sanskrit: punarbhava; Pali: punabbhava) to "reincarnation" as they take the latter to imply a fixed entity that is reborn. It is said to be the "evolving consciousness" (Pali: samvattanika viññana, M.1.256) or "stream of consciousness" (Pali: viññana sotam, D.3.105). that reincarnates. The early Buddhist texts make it clear that there is no permanent consciousness that moves from life to life. The lack of a fixed self does not mean lack of continuity. In the same way that a flame is transferred from one candle to another, there is a conditioned relationship between one life and the next: they are neither identical nor completely distinct.
While all Buddhist traditions seem to accept some notion of rebirth, there is no unified view about precisely how events unfold after the moment of death. The medieval Pali scholar Buddhaghosa labeled the consciousness that constitutes the condition for a new birth as described in the early texts "rebirth-linking consciousness" (patisandhi). Some schools conclude that karma continued to exist and adhere to the person until it had worked out its consequences. For the Sautrantika school each act "perfumed" the individual and led to the planting of a "seed" that would later germinate as a good or bad karmic result. Theravada Buddhism generally asserts that rebirth is immediate while the Tibetan schools hold to the notion of a bardo (intermediate state) that can last up to forty-nine days. This has led to the development of a unique 'science' of death and rebirth, a good deal of which is set down in what is popularly known as The Tibetan Book of the Dead.
Theravada Buddhism generally denies there is an intermediate state, though some early Buddhist texts seem to support it. One school that adopted this view was the Sarvastivada, who believed that between death and rebirth there is a sort of limbo in which beings do not yet reap the consequences of their previous actions but may still influence their rebirth. The death process and this intermediate state were believed to offer a uniquely favourable opportunity for spiritual awakening.
Another view of rebirth describes the cycle of death and birth in the context of consciousness rather than the birth and death of the body. In this view, remaining impure aggregates, skandhas, reform consciousness.
Buddhist meditation teachers suggest that observation reveals consciousness as a sequence of conscious moments rather than a continuum of awareness. Each moment is an experience of an individual mind-state such as a thought, a memory, a feeling or a perception. A mind-state arises, exists and, being impermanent, ceases, following which the next mind-state arises. Thus the consciousness of a sentient being can be seen as a continuous series of birth and death of these mind-states. Rebirth is the persistence of this process.
In the practice of Vipassana meditation, the meditator uses "bare attention" to observe the endless round of mind-states without interfering, owning or judging. This limits the power of desire which, according to the second noble truth of Buddhism, is the cause of suffering (dukkha) and leads to Nirvana (nibbana, vanishing (of the self-idea)).