Western scholars: Did the Buddha not speak the Digha Nikaya?

The Digha Nikaya has so many contradictions. I might take days so to finish this post.

1. DN 11 (which similar to MN 49 is anti-Brahmanistic propaganda addressed to Brahmans) refers to a 'consciousness without feature that occurs when nama-rupa is destroyed'. However, the core suttas (MN 9; SN 12.65; SN 12.67; etc) say consciousness cannot exist without nama-rupa. This is a contradiction, which supports the claim of the Western scholars that the DN was composed as propaganda for converting Brahmans. It also supports the intelligent view that 'nama-rupa' in the DN has the old Brahmanistic meaning rather than the Buddhist meaning. There can be a consciousness without 'naming-forms' but there cannot be a consciousness without mind-body.

2. DN 15 defines 'nama-rupa' in the old Brahmanistic way; and not the new Buddhist way found in SN 12.2; MN 9, etc. This is a contradiction.

3. In AN 3.61, the Buddhist lists the sense bases as one of his four teachings. But DN 15 does not even include the sense bases. To have nine conditions for Dependent Origination but exclude the sense bases is a contradiction.

4. DN 15 does not define 'aging & death' and gives a biological rather than mental description of 'jati'. SN 12.2 defines 'jati' as the production of 'beings' ('satta'). SN 5.10 and SN 23.2 define 'a being' as a view or idea. Therefore, DN 15 does not provide for a proper interpretation of 'jati'.

5. DN 15 does not define the six-fold consciousness but refers to a consciousness entering in a womb; which is not taught anywhere else in the suttas. This is a contradiction.

6. DN 27 gives a biological origin of the world account; where SN 12.44 and AN 4.45 say the world originates from sense contact. This is a contradiction.

In the interest of Buddha dhamma:-

DN 11 (which similar to MN 49 is anti-Brahmanistic propaganda 
addressed to Brahmans) refers to a 'consciousness without feature 
that occurs when nama-rupa is destroyed'.

In DN 11 (Kevatta Sutta), quoting from Maurice Walshe's translation, substituting the ambiguous "consciousness" with vinanna:-

And the answer is:
Where vinanna is signless, boundless, all-luminuous,
That's where earth, water, fire and air find no footing,
There both long and short, small and great, fair and foul,
There namarupa are wholly destroyed,_
With the cessation of vinanna, this is all destroyed.

You missed the last line - the vinanna's cessation.

Many experienced human meditators, while they are still alive and kicking, have "seen" this vinanna that is signless, boundless, luminous. It can never be seen via thinking and reading. And it is "there", eventually, and finally, at the expiration of that individual's present karmic "life forces", that the final liberation is won, i.e., the next namarupa cannot come into being.

I do not wish to cause ill-will and unease by writing point-by-point counter-reply to the other statements you had made in your answer to your own question.

However, should your intention be skillful, i.e., to know others' opinion so that you have some answers to your many questions, you may wish to ask your questions separately. On the contrary, if you had come to your own conclusions, this forum may not be the correct place as it is a question-answer platform.

My apology for offering an unsolicited advice/opinion. Upon reading your reply to your own question, I know that many of your doubts can be cleared with meditation practise. Thereafter, you will be too "occupied" trying to match your experience/insight with the Abhidhamma. Ehipassiko.

May you quickly find unconditioned inner peace.

Is there any evidence in the suttas showing the Buddha was "flexible" in his teaching of Dhamma? Or do the suttas show the Buddha wished his teachings to remain consistent & clearly representative of what he taught?

I think the Buddha explained Dhamma, and that the explanation was adapted according to who he was addressing.

This footnote to the Sigalovada sutta, for example, suggests that "worshipping the six directions" was a Vedic ritual, and the Buddha takes advantage of the occasion to teach a different doctrine.

But that's not to say that the doctrine is incompatible with the doctrine taught in other suttas (but it is rather different to the Rhinoceros sutta for example).

Or according to Piya Tan the Aggañña Sutta (DN 27) is addressed to Brahmins (i.e. probationary monks who were Brahmins) and is perhaps a parody of Brahminical creation myths. The subject matter is "fantastic" but the doctrine (i.e. that the fall is due to craving "nourishment") is again not incompatible with other suttas.

I don't mean to generalise about the whole Digha Nikaya. But you ask whether he was "flexible, or, wished to remain consistent" -- perhaps he was flexible 'and' remained consistent.

I think that's famously part of his ability as Buddha, i.e. to know how to teach different people.

One of the suttas which shows that "the Buddha wished his teachings to remain consistent & clearly representative of what he taught" is (perhaps ironically, given the question) the Maha-parinibbana Sutta i.e. DN 16 -- which includes the "four great references" and so on.

Incidentally in this answer Bonn says ...

I can answer the question if I still quote the original text from Tipitaka and Atthakatha without making them conflict with each other.

I never try to make Tipitaka conflict with each other, never make Atthakathā conflict with each other, and never cut any part of Tipitaka and Atthakathā off.

... and in this answer ...

People who can understand the noble truth from tipitaka must can deconflict every uncleared word of tipitaka

... so I presume it's possible that, I think it's the opinion of e.g. Thai/Buddhist scholars that, the teachings are consistent.

In my opinion though (I don't know about Bonn's) to say "they're consistent" might need some flexibility (and good-will, and if not 'faith' exactly then at least a willingness to listen) in how you interpret them -- words have a range of meanings, they're often used metaphorically, part of the doctrine is not being over-attached to specific views, I think they are adapted/suited to the specific audience (often a reply to a specific question), etc.

Perhaps my opinion (above) is overly rosy though, and there are bits (of suttas) -- not all in the Digha Nikaya -- which I overlook or ignore. I don't think I'd want to argue the doctrinal details you identify in your answer -- some of your comments (e.g. about namarupa) I just don't understand or have no opinion about; and some (e.g. about DN 27) isn't how I read that sutta (and I'm content with my reading of it but I'm not sure it would benefit anyone to try to argue about it with you).

Is there evidence (such as contradictions with other suttas)
suggesting the Buddha did not speak the Digha Nikaya?

The four primary Theravadin Nikayas, namely Digha Nikaya, Majjhima Nikaya, Samyutta Nikaya, and Anguttara Nikaya contained no contradiction with each other.

You may also wish to scrutinize the Buddhist Councils "convention" and their outcomes to ascertain the level of "authenticity"/preservation of the Buddha's teachings.

In there any evidence in the suttas where the Buddha said he would 
teach a different modified Dhamma ("propaganda") merely for the 
purpose of converting Brahmins & other outsiders?

In the suttas, the Buddha pretty much taught the same thing to everyone. There was no "special" teachings for select groups of disciples or audiences.

Is there any evidence in the suttas showing the Buddha was "flexible"
in his teaching of Dhamma? Or do the suttas show the Buddha wished 
his teachings to remain consistent & clearly representative of what 
he taught?

The Buddha had over 40 years to teach. So, he did teach the same thing in many ways depending on the intellectual level of his listeners. And he had 40 years to admonish/correct disciples who developed wrong views of his teachings.

It was the Buddha who spoke the words of the DN, but it was compiled, collated, arranged and rearranged by the Sangha centuries after his passing. The DN was not fabricated. Also the Buddha certainly never said, "Today I'm going to speak Digha Nikaya 1".

The Sangha may have rearranged the suttas into the sequence of the DN today with intention to define the difference between the Buddha's teachings and other religions (in DN 1), the role of the monks (in DN 2), the role of the lay followers (in DN 31), the continuation of Buddhism after the Buddha passes away (in DN 16) etc. There might have been some specific intention behind this arrangement, perhaps to create a constitution of sorts.

OP: Is there evidence (such as contradictions with other suttas) suggesting the Buddha did not speak the Digha Nikaya?

There is no evidence of contradiction between the nikayas.

OP: In there any evidence in the suttas where the Buddha said he would teach a different modified Dhamma ("propaganda") merely for the purpose of converting Brahmins & other outsiders?

No. The Buddha taught the same thing to monks, lay followers and outsiders, according to SN 42.7:

“To me, the monks and nuns are like the good field. I teach them the Dhamma that’s good in the beginning, good in the middle, and good in the end, meaningful and well-phrased. And I reveal a spiritual practice that’s entirely full and pure. Why is that? Because they live with me as their island, protection, shelter, and refuge.

To me, the laymen and laywomen are like the average field. I also teach them the Dhamma that’s good in the beginning, good in the middle, and good in the end, meaningful and well-phrased. And I reveal a spiritual practice that’s entirely full and pure. Why is that? Because they live with me as their island, protection, shelter, and refuge.

To me, the ascetics, brahmins, and wanderers who follow other paths are like the poor field, the bad ground of sand and salt. I also teach them the Dhamma that’s good in the beginning, good in the middle, and good in the end, meaningful and well-phrased. And I reveal a spiritual practice that’s entirely full and pure. Why is that? Hopefully they might understand even a single sentence, which would be for their lasting welfare and happiness.

So, he did not teach followers and non-followers differently..

OP: Is there any evidence in the suttas showing the Buddha was "flexible" in his teaching of Dhamma? Or do the suttas show the Buddha wished his teachings to remain consistent & clearly representative of what he taught?

WHAT he taught was the same, but HOW he taught it, could be different according to the Kesi Sutta (AN 4.111):

"Kesi, I train a tamable person [sometimes] with gentleness, [sometimes] with harshness, [sometimes] with both gentleness & harshness.

"In using gentleness, [I teach:] 'Such is good bodily conduct. Such is the result of good bodily conduct. Such is good verbal conduct. Such is the result of good verbal conduct. Such is good mental conduct. Such is the result of good mental conduct. Such are the devas. Such are human beings.'

"In using harshness, [I teach:] 'Such is bodily misconduct. Such is the result of bodily misconduct. Such is verbal misconduct. Such is the result of verbal misconduct. Such is mental misconduct. Such is the result of mental misconduct. Such is hell. Such is the animal womb. Such the realm of the hungry shades.'

"In using gentleness & harshness, [I teach:] 'Such is good bodily conduct. Such is the result of good bodily conduct. Such is bodily misconduct. Such is the result of bodily misconduct. Such is good verbal conduct. Such is the result of good verbal conduct. Such is verbal misconduct. Such is the result of verbal misconduct. Such is good mental conduct. Such is the result of good mental conduct. Such is mental misconduct. Such is the result of mental misconduct. Such are the devas. Such are human beings. Such is hell. Such is the animal womb. Such the realm of the hungry shades.'"

"And if a tamable person doesn't submit either to a mild training or to a harsh training or to a mild & harsh training, what do you do?"

"If a tamable person doesn't submit either to a mild training or to a harsh training or to a mild & harsh training, then I kill him, Kesi."

"But it's not proper for our Blessed One to take life! And yet the Blessed One just said, 'I kill him, Kesi.'"

"It is true, Kesi, that it's not proper for a Tathagata to take life. But if a tamable person doesn't submit either to a mild training or to a harsh training or to a mild & harsh training, then the Tathagata doesn't regard him as being worth speaking to or admonishing. His knowledgeable fellows in the holy life don't regard him as being worth speaking to or admonishing. This is what it means to be totally destroyed in the Doctrine & Discipline, when the Tathagata doesn't regard one as being worth speaking to or admonishing, and one's knowledgeable fellows in the holy life don't regard one as being worth speaking to or admonishing."