- an individual's past actions can affect one's future lives or reincarnations.
The word karma refers to both the action itself and the resulting effects. This doctrine first appeared in the Upanishads, which accompany the sacred spiritual Hindu texts, the Vedas. The Chandogoya Upanishad states:
"Those whose deeds in former lives were good get desirable lives such as those of Brahmans (priests), Kshatriyas (warriors), or Vaisyas (merchants and farmers). Those whose lives are bad get lives such as those of Candalas, dogs or swines."
And in the Brhadaranyaka Upanishad, it says:
"A man of good acts will become good, a man of bad acts, bad. He becomes pure by pure deeds, bad by bad deeds."
However, the philosophy of karma is a bit more complex. The idea of karma is rooted in that of transmigration, that each life is just a link in a chain of successive lives. The karma in the last life determines the success in the next. This is used to explain the inequality of people in society (the caste system).
The theory of karma instructs that the atman (self), whether a person or an animal or even a god, has existed without a beginning as the location for one's experiences and deeds. Any action which is done during a life produces traces which carry the atman along with them. When an atman dies, after a brief time in heaven or hell, the karmic traces from the past life manifest and determine the three futures of the self: human, animal or god. They also determine the longetivity of the next life and the experiences that self may encounter. After determination is complete, these karmic traces are completely removed, only to be replaced by new ones acquired during the next life. Thus, one cannot improve one's status in a given life, but only through reincarnation, live a better subsequent life. The only way to end this cycle is to perfect oneself until you have reached the highest state of god (Bramha) and leave the cycle of birth-life-death.
These ideas are also part of the doctrine in Buddhism and Jainism. Bhuddists view karma as simply cause and effect. Jains see karma as a substance that also produces the chain of birth and death.
paraphrased from: The Dictionary of Global Culture, Kwame Appiah & Henry Gates, Jr.