Bruce Matthews notes that there is no cohesive presentation of karma in the Sutta Pitaka, which may mean that the doctrine was incidental to the main perspective of early Buddhist soteriology. Schmithausen is a notable scholar who has questioned whether karma already played a role in the theory of rebirth of earliest Buddhism.[page needed][note 32] According to Vetter, "the Buddha at first sought "the deathless" (amata/amrta), which is concerned with the here and now. According to Vetter, only after this realization did he become acquainted with the doctrine of rebirth." Bronkhorst disagrees, and concludes that the Buddha "introduced a concept of karma that differed considerably from the commonly held views of his time." According to Bronkhorst, not physical and mental activities as such were seen as responsible for rebirth, but intentions and desire.