Classical philosophers of the six darśanas in relevence to Vedā.
Sāṃkhya
In the Sāṃkhya philosophy, the idea that Vedas are from eternity is denied, because there is evidence for their production by knowledgeable and experienced sages/devas as they “know” the truth. In the case of ritual scriptures, (also dubbed as Vedas) they are not about any mysterious thing “beyond senses” but their efficacy rests on the principle of karma. Sāṃkhya also repels the notion that no human can ever instruct any knowledge of Vedas or that Vedas are superhuman and impossible to understand. Sāṃkhya argues that knowledge of Vedas is traditional, (and therefore people can instruct it without any issue) those who “know” can surely understand Vedas.
Sāṃkhya explains the “apauruṣeya” doctrine as that the knowledge of Vedas proceeds naturally and involuntarily from the knowing brahma, just like respiration, and not preceded by voluntary thought. Therefore, it is not a “creation” of any supreme man.
Pros : The theory of evolution, studying by classification, wise discrimination, stress on suffering and attainment of knowledge of oneself by detachment with the modes of nature. Rational arguments against dogmatic theism.
Cons : Later schools in Vedānta didn’t allow sāṃkhya to have cons on Indian culture – they appropriated best of ideas and reduced sāṃkhya.
Nyāya
Nyāya also disputes the notion that Vedas need to be from “eternity” to be authoritative. Its authority is accepted because of the expertise of the authors (sages), just like how Āyurveda (medical science) or Mantras are accepted – not through blind faith but because we are aware of the expertise of the relevant persons.
However, Akṣapāda Gautama argues that there is no ground for charging Brahmanical injunctions with tautology or contradictions or untruth, and whatever seems to be untruth is because the action has not been performed well.
Still, Nyāya established that Vedas are subjected to logic and reason – and this itched Mīmāṃsakas and their descendants, who declared the Naiyāyika hetuvādins to be heretics.
Pros: Reasoning, knowledge of logical fallacies, concept of arriving at truth through discussion, rationalism.
Cons : Often led to focus on winning debates and somehow establish one’s points. This was not mostly done by ancient Naiyāyikas, but the medieval ones who appropriated Nyāya systems for their own use. Nyāya also believed in a presence of a clear cause and effect instead of the sāṃkhya viewpoint that described it a spectrum of evolution from cause to effect. Developed a soft-corner towards the idea of God which would be taken for granted by later schools.
Vaiśeṣika
Vaiśeṣika as in Kaṇāda sūtra basically has no problem with the notion that Vedas are self-validated or that they are authoritative, but their authority is not established by the “eternality of sound” (śabda brahman is negated) – just like how Nyāya and Sāṃkhya deny. Vaiśeṣika doesn’t know of any “īśvara” to be the author of Vedas.
However, Vaiśeṣika says that the Vedas are devised with intelligence, because we see wisdom in them. In what Vedas hold as sanctified/pure, we see wisdom, in what they hold doṣa, we see hiṃsā in them. The authority of Vedas comes from the fact that they are part of an intelligent teaching of sages and their tradition, based on wise observances. This is opposed to the Sāṃkhya notion that Vedas are involuntary and not a product of intelligent thinking.
Pros : Naturalist philosophy, scientific attitude, concept of atoms.
Cons : No notable cons.
Yoga
Yoga as proposed by Patañjali doesn’t indulge in arguments about the origin of Vedas. And it says that blind following of word-knowledge or ritual injunctions is a distraction. The actual experiential knowledge of the ancients can still be attained through union of yoga, in meditation. Yoga is attainable through meditation on an Īśvara who represents omniscience and oneness of everything, (different from “God”) and this Īśvara is supposed to be the Ācārya of ancient sages. The eternal sound of praṇava is mentioned on which one shall meditate.
Pros : Mental well-being, power of mind and thinking, mindfulness, warnings regarding hair splitting over unnecessary things and bothering about unnecessary things.
Cons : Had a soft corner towards the ideas of supernatural powers earned through meditation, and also the idea of meditating on God, which would later be exploited by bhakti cults to apply to their personal Gods.
Mīmāṃsā
Mīmāṃsā was a radical ritualist system which held Vedas as not any more purposeful other than the ritual injunctions that could be developed from them. So, more than the verses, the ritual injunctions, brāhmaṇas and ritual context matters. Since the best right karma is “yajña” according to mīmāṃsakas, the karma as ritual validates itself and there is no need for an īśvara and Vedas are indeed self-validated because of the ritual injunctions alone. Mīmāṃsā has the most radical notion that Vedas existed from eternity, their eternity unquestionable. They are not produced or created by any person. The teaching establishes the eternity of Vedas because “sound is eternal”. (This was severely opposed by other schools, as we already saw) Mīmāṃsakas believed so much in the efficacy of the ritual that they maintained that even Devas mentioned in mantras don’t exist outside the mantra, and it is the mantra that produces the devas who bestow the fruit of the ritual.
Later mīmāṃsakas modify the nāda theories to suit the opponents, and seem to have succeeded – with Vedānta under Śaṅkara again modifying to bring nāda as a manifestation of an intelligent brahman.
The usual arguments we read by Buddha against the “Vedas” are against the mīmāṃsaka dogmas/beliefs and not against any of the Vedic sages.
Pros: Very systematic inquiry and methods to perform passionate study.
Cons: Dogmas related to Vedas, superstitions regarding rituals, ritualist fundamentalism.
Vedānta
In Vedānta, the Upaniṣads get the primary importance as the “jñāna kāṇḍa”, and their content is all explained off as brahman. For example, one might see how Indra’s teaching in Kauṣītakī Āraṇyaka is explained off by Vedāntins, so is Kṛṣṇa’s teaching in Gītā, as these persons united with brahman teaching about brahman. So, sages are also viewed in this way. The Vāmadeva’s famous sūkta for instance is viewed as his “realization” with brahman. Thus, the popular theory of sages being realized with brahman and their “vision” being Vedas is born from Vedānta.
Pros: Inclusiveness
Cons: Vedas completely removed from picture, obsession with brahman and megalomaniac projections of reality. Appropriation of other cults to decimate them ultimately.
All Vedic devas are manifestations of brahman, Vedas themselves are so.
Mīmāṃsā and Vedānta see Oṃkāra as the primordial nāda on which sounds (esp. of Vedas) are built, however Śaṅkara seems to imply that the nāda is not eternal in the sense it will merge with brahman at the time of dissolution, however those who meditate on nāda can attain brahman.
Disclaimer: The post is based mostly on the original and initial viewpoints of the philosophical schools. With the evolution of thoughts and the defensive mechanism triggered by the “nāstika” schools, the classical philosophers have tried to interpret their theories in a different light.
Nirīśvara and Nāstika.
A nirīśvara is someone who doesn’t believe in a creator God who is “beyond” this “creation”. It is different from atheism in the sense the person might advocate the worship/adoration of natural entities and concepts which can actually affect your mind and life. Sāṃkhya is strongly nirīśvara, you might call it atheist in the sense today theism refers to belief in supernatural “G”od(s). It is not nāstika.
Nāstika is a pejorative term used to label the deniers of Vedas or Vedic sages or certain tenets which the mainstream believes in. (Something like “heresy”) Quite contrary to popular perception, Buddha never criticized the sages themselves, and Jains were once against getting labeled nāstikas by the mīmāṃsakas and tried to locate Ṛṣabhadeva and Ariṣṭanemi in Vedic/Brahmanic literature to support themselves. The only pure nāstikas which all of them accused were the Cārvākas or Lokāyatas who were more like hedonists and propagated rumours that Vedas are composed by demons.
Therefore, the Sankya, Nyaya and Vaisheshika are Nasthika schools and not Asthika schools as believed by Kiron.
I didn’t invent anything on my own, and neither do you have the right to invent labels all by yourself. I am quoting the popular opinion in the medieval ages by the mīmāṃsaka-Vedāntins, as reflected in works like Sarvadarśanasaṃgraha.