Finding Authentic Suttas

The trouble with the question is that it uses a very vague term: "authenticity". We don't really know what this means to the questioner. And it is likely that it means different things to different people.

From a scholars point of view, if authentic means that the texts are what they themselves say they are, the there are probably no authentic texts. If authentic means, texts that were accepted as authentic by a Buddhist tradition at some point, then almost everything written is authentic.

Not that authenticity is a trivial issue for Buddhists. One could go as far as to say that it is an obsession. But authenticity is not so much a part of the scholarly approach to texts. A scholar may try to pin down the provenance of a text, but whether knowing this makes a text authentic or not is probably not an issue for a scholar.

For example, I work on the Heart Sutra. Since Jan Nattier's 1992 article on it, the Heart Sutra is now widely regarded, by scholars though not religieux, as having been compiled in China from quotations from other sutras, mainly the 25,000 line Perfection of Wisdom text, in Kumārajīva's Chinese translation. This probably happened ca. 7th century. It was later translated into Sanskrit, and then added to leaving a short text and a long text.

For religieux the text is authentic because they saw it has having a Sanskrit "original" and because centuries of teaching lineages proclaimed it "authentic". Scholar's now think that Mahāyāna texts were composed in Middle-Indic and translated into Sanskrit in the 4th or 5th century (during the Gupta Empire the use of Sanskrit as a literary language was widespread in North India). So having a Sanskrit text no longer signifies authenticity. Having a Gāndhārī text is more likely to be considered a measure of antiquity and therefore authenticity.

On the other hand the Heart Sutra seems to an authentic product of the Buddhist milieu in 7th century China which combined the cult of Avalokiteśvara, with study of Perfection of Wisdom, and the use of magic spells for protection (Pāḷi parrita; Skt dhāraṇī).

Ironically the long Sanskrit Heart Sutra which has the traditional trappings of authenticity (eg. it begins एवं मया श्रुतं) is now seen as less authentic because it's apparent that the standard sutra beginning was added later. The short text is more authentic because it is closer to the original Chinese versions.

Until recently the Chinese version attributed to Xuanzang (T251) was considered more authentic, but Nattier cast doubt on the attribution so now it seems less authentic. Indeed the version attributed to Xuanzang (T251) or the version attributed to Kumārajīva (T250) can not have been the product of these men, and neither of them can have been the model for the extant Sanskrit version. So the original text, the most authentic text, is actually missing. No attempt has yet been made to reconstruct the original (though I think it ought to be possible). But then the question of how authentic a reconstructed text would be is a big one.

For more than 60 years the Sanskrit text, edited and published by Edward Conze in 1948 and revised in 1967, was considered the authentic Sanskrit Heart Sutra. Conze compared many manuscripts and tried to imagine what the author had intended. But Conze made a number of mistakes (one of which I identified and corrected in my 2015 article for the JOCBS). So Conze's edition, long treated as the authentic Heart Sutra must now considered rather inauthentic - indeed Conze's version is a badly edited version of a poor translation of a Chinese text.

It's apparent that authentic is a very difficult concept to pin down. What it might mean to a scholar is quite different from what it might mean to a religieux. A Theravādin will most likely not consider any Mahāyāna texts as authentic. But then most scholars don't find the Theravādin idea of "authentic" meaningful - it's wholly an insider perspective.

Authenticity is important to religious sectarians primary, In my opinion, because they are involved in a competition for resources with other sects (Buddhist and non-Buddhist). "Authenticity" is like a seal of approval. For lay Buddhists it is a means of ensuring maximum merit from generosity to religious organisations. For monastic Buddhists it helps to ensure their continued hegemony and control of resources. In terms of the study of texts none of this is very relevant. I can't be sure, but in eight published articles on Buddhist texts I don't think I have used the word authentic or any derivative of it. It's just not a very interesting concept.

Check out the paper/book called "The Authenticity of Early Buddhist Texts":

https://ocbs.org/wp-content/uploads/2015/09/authenticity.pdf

The short answer is that there are many ways spanning multiple disciplines that scholars use in an attempt to determine authenticity.

With that being said, scholars are beings, the same way the Buddha is a being. It's up to an individual to figure out who they wish to listen to and heed.

I think the Mahapadesa sutta found within the Mahaparinibbana sutta (DN 16) as shared by the individual above seems like the most reliable guide.

I also think what scholars say is definitely important, but secondary to this.

But again, it's up to the individual to voluntarily choose which individual or group to pay attention to and heed the most.

Traditionally, the criteria for teaching authenticity are:

• it must not contradict the observable facts and laws of nature,
• it must not contradict commonly recognized moral rules,
• it should lead to letting go, cooling down, emancipation, liberation,
• it should be traceable to a remark made in the suttas, preferably in multiple places.

In Theravada, the criteria for accepting any teaching as authentic is based on Mahapadesa sutta, also found in Mahaparinibbana sutta and Nettipakarana. Accordingly, any Dhamma that's heard as a Buddha's statement must be verified with the suttas and the vinaya.

This also indicates that the authority increases from a single monk to a group of monks, and the highest authority is given to the words directly heard from the Buddha. Even so, it must be cross checked with the suttas and vinaya to see if they were interpreted correctly.

Then the Blessed One said: "In this fashion, bhikkhus, a bhikkhu might speak: 'Face to face with the Blessed One, brethren, I have heard and learned thus: This is the Dhamma and the Discipline, the Master's Dispensation'; or: 'In an abode of such and such a name lives a community with elders and a chief. Face to face with that community, I have heard and learned thus: This is the Dhamma and the Discipline, the Master's Dispensation'; or: 'In an abode of such and such a name live several bhikkhus who are elders, who are learned, who have accomplished their course, who are preservers of the Dhamma, the Discipline, and the Summaries. Face to face with those elders, I have heard and learned thus: This is the Dhamma and the Discipline, the Master's Dispensation'; or: 'In an abode of such and such a name lives a single bhikkhu who is an elder, who is learned, who has accomplished his course, who is a preserver of the Dhamma, the Discipline, and the Summaries. Face to face with that elder, I have heard and learned thus: This is the Dhamma and the Discipline, the Master's Dispensation.'

"In such a case, bhikkhus, the declaration of such a bhikkhu is neither to be received with approval nor with scorn. Without approval and without scorn, but carefully studying the sentences word by word, one should trace them in the Discourses and verify them by the Discipline. If they are neither traceable in the Discourses nor verifiable by the Discipline, one must conclude thus: 'Certainly, this is not the Blessed One's utterance; this has been misunderstood by that bhikkhu — or by that community, or by those elders, or by that elder.' In that way, bhikkhus, you should reject it. But if the sentences concerned are traceable in the Discourses and verifiable by the Discipline, then one must conclude thus: 'Certainly, this is the Blessed One's utterance; this has been well understood by that bhikkhu — or by that community, or by those elders, or by that elder.' And in that way, bhikkhus, you may accept it on the first, second, third, or fourth reference. These, bhikkhus, are the four great references for you to preserve."
Mahāpadesā sutta