Karma: action determines future rebirth

Hindus and Buddhists affirm karma: that morally weighted action bears fruit, shaping one's circumstances in this life and the conditions of future births. Textual historians trace a real development behind the idea: in the earliest Vedic sources, karma denoted ritual action itself, chiefly the correct performance of sacrifice, and its extension into a universal law of moral cause and effect governing every soul's fate across lifetimes is generally located by scholars in the Upanishadic period, when a mystical and ethical reading of ritual language displaced the older purely liturgical sense.

In the Hindu formulation developed in the Upanishads and taught in the Bhagavad Gita, one is bound by the consequences of desire-driven action and reaps what one sows across lifetimes, while acting without attachment to the fruits, the ideal of nishkama karma the Gita commends, can loosen that binding force even while action continues. Buddhism shares the principle of moral causation but reframes it around intention (cetana) rather than the bare deed, holding that an act's karmic weight lies in the volition behind it, and detaches the whole mechanism from any enduring self that carries the results forward, describing instead a causal stream of conditioned states.

Karma is one of the great ideas the Indian traditions hold in common while interpreting quite differently. For Hinduism it operates within a cosmos of enduring souls moving through samsara toward moksha; for Buddhism it functions without a permanent self, results passing on as a causal stream rather than accruing to a soul, a distinction Buddhist philosophers regard as one of their tradition's sharpest departures from its neighbors. Jain thought takes karma in a third and strikingly different direction, treating it not as a metaphor for moral consequence but as literally material: karma is subtle matter (karmic pudgala) that actually adheres to and weighs down the soul (jiva) in proportion to the harm done, a physicalist theory with no real parallel in Hindu or Buddhist accounts, where the mechanism is generally understood as a moral or psychological law rather than a substance.

Philosophers of comparative religion have long noted karma's resemblance, as an explanatory structure, to theodicies in other traditions, since it offers an account of undeserved suffering that does not require blaming a creator god, attributing present misfortune instead to unseen causes in one's own past. Critics both within and outside the traditions have asked whether such a law, operating across unremembered lives, can be tested or falsified in any ordinary sense, a question the traditions themselves generally answer by treating karma as a matter of scripture and spiritual insight rather than empirical demonstration.