Vedanta is distinctly antagonistic to Nyaya, and most of its powerful dialectic criticism is generally directed against it. S'a@nkara himself had begun it by showing contradictions and inconsistencies in many of the Nyaya conceptions, such as the theory of causation, conception of the atom, the relation of samavaya, the conception of jati, etc [Footnote ref 598]. His followers carried it to still greater lengths as is fully demonstrated by the labours of S'rihar@sa, Citsukha, Madhusudana, etc. It was opposed to Mima@msa so far as this admitted the Nyaya-Vais'e@sika categories, but agreed with it generally as regards the prama@nas of anumana, upamiti, arthapatti, s'abda, and anupalabdhi. It also found a great supporter in Mima@msa with its doctrine of the self-validity and self-manifesting power of knowledge. But it differed from Mima@msa in the field of practical duties and entered into many elaborate discussions to prove that the duties of the Vedas referred only to ordinary men, whereas men of higher order had no Vedic duties to perform but were to rise above them and attain the highest knowledge, and that a man should perform the Vedic duties only so long as he was not fit for Vedanta instruction and studies.
With Sa@mkhya and Yoga the relation of Vedanta seems to be very close. We have already seen that Vedanta had accepted all the special means of self-purification, meditation, etc., that were advocated by Yoga. The main difference between Vedanta and Sa@mkhya was this that Sa@mkhya believed, that the stuff of which the world consisted was a reality side by side with the puru@sas. In later times Vedanta had compromised so far with Sa@mkhya that it also sometimes described maya as being made up of sattva, rajas, and tamas. Vedanta also held that according to these three characteristics were formed diverse modificationsof the maya. Thus Is'vara is believed to possess a mind of pure sattva alone. But sattva, rajas and tamas were accepted in Vedanta in the sense of tendencies and not as reals as Sa@mkhya held it. Moreover, in spite of all modifications that maya was believed to pass through as the stuff of the world-appearance, it was indefinable and indefinite, and in its nature different from what we understand as positive or negative. It was an unsubstantial nothing, a magic entity which had its being only so long as it appeared. Prak@rti also was indefinable or rather undemonstrable as regards its own essential nature apart from its manifestation, but even then it was believed to be a combination of positive reals. It was undefinable because so long as the reals composing it did not combine, no demonstrable qualities belonged to it with which it could be defined. Maya however was undemonstrable, indefinite, and indefinable in all forms; it was a separate category of the indefinite. Sa@mkhya believed in the personal individuality of souls, while for Vedanta there was only one soul or self, which appeared as many by virtue of the maya transformations. There was an adhyasa or illusion in Sa@mkhya as well as in Vedanta; but in the former the illusion was due to a mere non-distinction between prak@rti and puru@sa or mere misattribution of characters or identities, but in Vedanta there was not only misattribution, but a false and altogether indefinable creation. Causation with Sa@mkhya meant real transformation, but with Vedanta all transformation was mere appearance. Though there were so many differences, it is however easy to see that probably at the time of the origin of the two systems during the Upani@sad period each was built up from very similar ideas which differed only in tendencies that gradually manifested themselves into the present divergences of the two systems. Though S'a@nkara laboured hard to prove that the Sa@mkhya view could not be found in the Upani@sads, we can hardly be convinced by his interpretations and arguments. The more he argues, the more we are led to suspect that the Sa@mkhya thought had its origin in the Upani@sads. Sa'a@nkara and his followers borrowed much of their dialectic form of criticism from the Buddhists. His Brahman was very much like the s'unya of Nagarjuna. It is difficult indeed to distinguish between pure being and pure non-being as a category. The debts of S`a@nkara to the self-luminosity of the Vijnanavada Buddhism can hardly be overestimated. There seems to be much truth in the accusations against S'a@nkara by Vijnana Bhik@su and others that he was a hidden Buddhist himself. I am led to think that S'a@nkara's philosophy is largely a compound of Vijnanavada and S'unyavada Buddhism with the Upani@sad notion of the permanence of self superadded.