[Rexaviennatutr]

There's two ways I would answer your question. The first is the Four Reliances:

“Do not rely on individuals, rely on the teachings.
Do not rely on the words, rely on the meaning.
Do not rely on the adapted meaning, rely on the ultimate meaning.
Do not rely on intellectual knowledge, rely on wisdom.”

Interesting. The first one seems to comport with the Buddha's admonition to not rely on "the monk is our teacher", but I am looking at a discussion of these "four reliances" ( http://www.rigpawiki.org/index.php?title=Four_reliances ), in which one Mipham Rinpoche says in "The Sword of Wisdom":

"When the teachings are well presented,
It does not matter what the speaker is like.
Even the bliss-gone buddhas themselves
Appear as butchers and such like to train disciples."

This seems to fail to comport with the Buddha's admonition to critically examine a teacher's conduct before deciding whether to take that teacher on.

The second seems to fail to take into account that the Buddha used words to illustrate his teachings, and admonished his followers to remember those very words. There is much repetition and rote learning portrayed in the suttas among the monks and from the Buddha himself. Words are used to convey meaning, of course, and the meaning, knowledge and understanding that is intended is indeed the important part, but words are necessary and sufficient to convey that meaning.

The third is a circular reference to the idea of "provisional vs. ultimate truth" that the Buddha did not teach. It might work for one who holds such a view, but such an idea is based in mere speculative view. This view is also based in the self-serving sectarian assumption that the Buddha's teachings are inferior to the tibetan religion's doctrines (again form "Sword of Wisdom):

"The omniscient one himself in all his wisdom,
Taught according to students’ capacities and intentions,
Presenting vehicles of various levels
Just like the rungs of a ladder."

This assumption is further illustrated by what follows:

"Wisely, he spoke with certain intentions in mind,
As with the eight kinds of implied and indirect teachings.
If these were to be taken literally they might be invalidated,
But they were taught for specific reasons."


There is a hotlink in this article to an explanation of the "eight kinds of implied and indirect teachings". What are these? Let us examine one or two of them:

"The indirect teachings aimed at introducing people to the path are those given to shravakas in order to introduce them to the path in a gradual way. They are taught in view of what is true on a relative level only. This includes, for example, teaching that there is no self of the individual, but that the phenomena of form and so on do exist."

And just who are these poor shravakas who the Buddha taught a supposed inferior, introductory set of teaching by virtue of their inferior capacities and intentions? There is a link provided, and it goes to this explanation:

"Shravaka (Skt. śrāvaka; Tib. nyenthö; Wyl. nyan thos) — a follower of the basic vehicle who strives to attain the level of an arhat. "

And what is this "basic vehicle"? Follow the link and we discover that it is a euphemism for our old friend, the denigration of the Buddha's own liberative teachings as being inferior "Hinayana":

"Basic Vehicle (Skt. Hīnayāna; Wyl. theg dman) — literally the 'Lesser Vehicle', but perhaps more accurately understood as 'Vehicle of Lesser Result'. What principally distinguishes followers of the Hinayana from those of the Great Vehicle (Skt. Mahayana; Wyl. theg chen) is their motivation. They aspire for the personal liberation of nirvana, and lack the courage to pursue the greater fruition of the Mahayana—this being the enlightenment of all sentient beings."

The fourth is based upon Advaitaist assumptions of dualism vs. non-dualism, rather than any teachings of the Buddha:

" When taking the definitive meaning into experience,
Do not rely upon the ordinary dualistic mind
That chases after words and concepts,
But rely upon non-dual wisdom itself.

That which operates with conceptual ideas
Is the ordinary mind, whose nature involves perceiver and perceived.
All that is conceived in this way is false
And will never touch upon the actual nature of reality."

Of course, the Buddha's teachings are not concerned with the nature of reality, rather on the causes of, and remedies for, suffering.

If a particular Mahayana/Vajrayana sutra is proven to be written after the time of the Buddha, do the Buddhist teachings contained within the sutra become automatically invalid?

The question appears invalid. If a particular teaching contradicts the teachings of the Buddha, and is shown to be not the words of the Buddha, it is obviously invalid. If a teaching comports with the Buddha's own liberative teachings, and explains the Buddhas liberative teaching(s) in a way that leads one to knowledge of the Buddha's teaching, it can be said to comport with the Buddha's teachings, though it cannot be said that it is a teaching of the Buddha, or that the Buddha spoke that teaching.

Can the teachings still be useful, valuable, as a part of the continuum of Buddhist thought?

They stand or fall depending on whether they comport with and convey the liberative teachings of the Buddha. At the same time, the liberative teachings of the Buddha stand on their own and are not in need of any expansion, and especially any embellishment.

Here's an interesting article I ran across the other day:

http://www.tricycle.com/feature/budd...-practitioners

Ms. Gross' propositions fail to take into account the practitioners who concern ourselves with the Buddha's own teachings, and who discard tangential and irrelevant teachings and methods regardless of from which school they are derived. It may provide solutions for some of the sectarian in-fighting between each of the "Yanas", but with very few exceptions, all three have departed from the Buddha's liberative teachings, and thus from the Buddha's liberative Path.