Appendix B: The "Ethicization of Reincarnation."
The anthropologist Gananath Obeyesekere has elucidated the logic of karma. He shows that reincarnation has been accepted in many cultures -- including the Trobriand Islanders, Balinese, West Africans, Australian aborigines, Amerindians, Inuit, Siberians, Asians, and the ancient Greek followers of Pythagoras and Plato. Always there is the belief that a soul goes to some other place after death for an indefinite period but must always return to this world by rebirth. In many cultures it is believed possible to change species when incarnating. By far the most common idea is that souls normally and preferably are reborn repeatedly into their own kinship group.
However, in a few societies one's next rebirth is determined by karma instead of kinship. The fortunes or misfortunes of this life occur in proportion to one's morality or immorality in previous lives. You will automatically receive just compensation for your deeds. No god need be involved in meting out those rewards and punishments. Karma is simply a law of the universe.
This notion of karma, Obeyesekere believes, arose only once: in India before the sixth century BCE. As we have seen, the Axial Age was marked everywhere by the development of rationality and ethics in religious thought. Until then, the term karma (which means "action") had referred only to ritual acts that lacked ethical implications. But beginning with one sacred Upanishad text, we see a change. A passage referring to the afterlife says, "A man turns into something good by good action and into something bad by bad action." Thus began the Hindu ethical doctrine of karma. A hundred years later, still in India, Mahavira animated the Jain faith and the Buddha began teaching his own new religious message, both of them employing this new concept of karma.
Obeyesekere calls this innovation the "ethicization" of reincarnation. Naturally, every society has moral rules but, with ethicization, the quality of one's afterlife became contingent on the practice of social ethics. However, to Buddhists, though not to Jains, it is not the objective consequences of one's actions that generate good or bad karma, but one's good or bad intentions when acting.
This theory that one's morality determines one's rebirth did not spread everywhere in the world. Most societies that believe in reincarnation continue to suppose that one is reborn into one's own family, regardless of one's accrued merits or demerits. Likewise there are considerable differences between societies in terms of how many reincarnations can be expected. In some societies, it is thought that the number of rebirths is limited but elsewhere (especially in Buddhism) it is believed that we go on being reborn forever, for the world had no beginning and will have no end. There never was a creator god because there was no creation.
For Asians during the Axial Age, the prospect of infinite rebirths offered no comfort. The reality, to them, was that life is suffering and that one's only hope is to escape the karmic wheel of endless rebirths. That, indeed, is the program offered by the Axial Age Indic religions. Nirvana (in Hinduism, moksha) is the ultimate insight that dissolves one's karma so that one can let go of the attachments binding one to life and rebirth. One becomes a Buddha, though none of the great religious teachers made it clear what would happen after that.
But as Buddhism developed over the centuries, especially in northern Asia, the notion grew that to escape from rebirth is a bit selfish. An enlightened one would prefer to remain in this world as a "Bodhisattva" and help others escape too. This aspiration distinguishes Mahayana Buddhism from the Theravada tradition, in which each person must find his own salvation, his release from karma and the endless succession of rebirths.
 Gananath Obeyesekere, Imagining Karma: Ethical Transformation in Amerindian, Buddhist, and Greek Rebirth (Berkeley: University of California Press, 2002), pp. 2-3.
 That atheistic premise characterizes Buddhism and Jainism, but not Hinduism, which teaches that upon attaining moksha one rejoins Brahman, the godhead.