The Middle Length Discourses of the Buddha - Bhikkhu Nanamoli [22]
The samaṇas were a much more diversified group which, lacking a common scriptural authority, promulgated a plethora of philosophical doctrines ranging from the diabolical to the superdivine. The Pali Canon frequently mentions six teachers in particular as contemporaries of the Buddha, and as they are each described as “the head of an order…regarded by many as a saint” (MN 77.5), they must have been quite influential at the time. The Majjhima Nikāya mentions both the set of six and, separately, states their individual doctrines; it does not, however, correlate the names with the doctrines. The connections between names and doctrines are made in the Sāmaññaphala Sutta of the Dīgha Nikāya.
Pūraṇa Kassapa, who is always mentioned first in the list, taught a doctrine of inaction (akiriyavāda) that denied the validity of moral distinctions (MN 60.13, MN 76.10). Makkhali Gosāla was the leader of the sect known as the Ājīvakas (or Ājīvikas), which survived in India down into the medieval period. He taught a doctrine of fatalism that denied causality (ahetukavāda) and claimed that the entire cosmic process is rigidly controlled by a principle called fate or destiny (niyati); beings have no volitional control over their actions but move helplessly caught in the grip of fate (MN 60.21, MN 76.13). Ajita Kesakambalin was a moral nihilist (natthikavāda) who propounded a materialist philosophy that rejected the existence of an afterlife and kammic retribution (MN 60.5, MN 76.7); his doctrine is always cited by the Buddha as the paradigmatic instance of wrong view among the unwholesome courses of action. Pakudha Kaccāyana advocated an atomism on the basis of which he repudiated the basic tenets of morality (MN 76.16). Sañjaya Belaṭṭhiputta, a sceptic, refused to take a stand on the crucial moral and philosophical issues of the day, probably claiming that such knowledge was beyond our capacity for verification (MN 76.30). The sixth teacher, the Nigaṇṭha Nātaputta, is identified with Mahāvīra, the historical progenitor of Jainism. He taught that there exists a plurality of monadic souls entrapped in matter by the bonds of past kamma and that the soul is to be liberated by exhausting its kammic bonds through the practice of severe self-mortification.
Whereas the Pali suttas are generally cordial but critical towards the brahmins, they are trenchant in their rejection of the rival doctrines of the samaṇas. In one sutta (MN 60) the Buddha contends that the firm adoption of any of the first three doctrines (and by implication the fourth) entails a chain of unwholesome states