The classical idea is that the Mahayana sutras the Buddha spoke were preserved by bodhisattvas and other beings in different realms and then revealed at later times as needed.
The modern idea is that the mahayana sutras were a forum for extra-agamic debates happening across the various schools, using the sutra format to authenticate their ideas.
My own take is a bit of both. My picture is something along these lines (bear in mind, my narrative assumes the mahayana sutras are authentic dharma, so adjust your lenses accordingly): After the time of the Buddha, not everyone congretated into neatly lined schools and the like. Geographical isolation and the like could easily create situations where communities of bhikshus would form around a lineage of highly realised beings, that originated around arhats that might have received only a few choice teachings from the Buddha before going off on their own. As they did not have contact with the wider community who invested the resources to establish a set canon of the Buddha's teachings, these people might formulate the teachings in different ways that didn't chime with how the established orthodoxy interpreted the teachings, as they relied mostly on their own realisation and went on their own conceptualisations of this to express it. Probably quite a few of these groups were also interacting with classes of enlightened beings beyond the human realm.
All of this is of course predicated on a 'handful of leaves' notion, that is to say although the Buddha laid bare all the necessary tools to become liberated he did not not teach all the possible ways of expressing this and did not express the wider implications of liberation or of how this took place in other realms. Included in this, was the way to become a buddha.
So fastforward a few hundred years of these groups developing like this and you can imagine what would happen when some wandering Vibhajjavadin, who was wellschooled in the canon that had been established and studied in the commentarial tradition that had grown around it, stumbled across a group like this who had developed a dharma rethoric along the lines of 'minds are not minds, they are called mind, neither past, present or future mind can be grasped' and furthermore, claimed to have a hotline to some Buddha they called Ashokbya in the eastern direction along with a select few 'bodhisattva' beings, apparently in training to become Buddhas that they were getting kinds of 'pure vision' from, teaching the Dharma. And that these people were aspiring for the same(!). Well, one can hardly blame such a bhikshu for thinking this was total adharma.
Actually, it's not quite so black and white. A lot of the notions we think of as being Mahayana today, such as the status of the Buddha, the two truths, the view of emptiness, upaya and such developed among the 18 early schools. There was clearly very different ideas going around of what the Buddha really meant based on the early sutras in the early schools. But there were also a lot of developments going in very different directions than this, primarily the abidharmic literature being developed by the Vibhajjavadins and Sarvastivadins.
In that scenario, the purpose of the mahayana sutras were twofold. One was to establish the actual meaning of the Buddha's teachings (a project everybody were busying themselves with). For example, the prajnaparamita sutras show very distinct traits of implicitly dialoguing with the realist teachings of the sarvastivadin abidharma. The other was to reveal the implications and variety of dharma-related phenomena left unsaid by the Buddha as being authentic expressions of the Dharma. For example, Nagarjuna is said to have received the Avatamsaka sutras from a group of nagas. That could refer to intelligent serpents, but naga is also en epithet of wise ones, so perhaps a theory that might appeal more to modern sensitivities is that he received it from just such a group as I've postulated here. The avatamsaka btw is what I would class very definitely as a 'pure vision' sutra, ie a teaching received from a Buddha with a very clearly structure and purpose for delineating the dharma in a specific way.
I think a work like the biography of Ajahn Mun is a good modern snapshot of how such 'proto-mahayana' developments might have taken place. Here's a meditation master, who spent a lot of his time on the fringes of Buddhist society in the forest with forest masters (not unlike how it is believed the prajnaparamita groups developed), chatting up Buddhas in other realms, receiving teachings from 'deceased arhats' and describing how what he learned about reality every day since becoming an arhat was vaster than could ever be described in scripture.
This is more or less how I see the early mahayana developments. At the end of the day, I think if one has an intuition that the mahayana sutras were spoken by enlightened beings, I think it holds up. If not, it can be substituted for the deluded misapprehensions of mystics who had strayed from the Dharma. But I think these basic intuitions and inclinations are generally the only worthwhile basis for determining whether the Mahayana is authentic or not, unless of course you're an arhat with the divine eye and such and can check up on it yourself.
Last edited by Anders
on Fri Jan 16, 2009 10:57 am, edited 1 time in total.