Early Buddhism
The concept of karma may have been of minor importance in early Buddhism. Schmithausen has questioned whether karma already played a role in the theory of rebirth of earliest Buddhism, noting that "the karma doctrine may have been incidental to early Buddhist soteriology." Langer notes that originally karma may have been only one of several concepts connected with rebirth. Tillman Vetter notes that in early Buddhism rebirth is ascribed to craving or ignorance. Buswell too notes that "Early Buddhism does not identify bodily and mental motion, but desire (or thirst, "trsna"), as the cause of karmic consequences." Matthews notes that "there is no single major systematic exposition" on the subject of karma and "an account has to be put together from the dozens of places where karma is mentioned in the texts," which may mean that the doctrine was incidental to the main perspective of early Buddhist soteriology.