Thank you very much, Malcolm. That's sorted a lot of things out for me and I see exactly where you are coming from. I can also see why many religious institutions have reacted badly to the Dzogchen teachings - it seems to be something that could act as an aqua regia to any formal power structure.
Yes, the archtypal bad reaction is when "500" Nalanda panditas travelled to Oḍḍiyāna to bully an 8 year old kid when they heard he was teaching that liberation was beyond cause and result. We know the rest of that story.
Tibetan power structures have been trying to keep the lid on Dzogchen ever since it entered into Tibet. Vairocana was banned to Eastern Tibet by a spurned queen and ministers who did not approve of Dzogchen. For example the 11th century translator Go Khugpa Lhatse accuses Vairocana of forging the five sems sde lungs, accuses Nubchen of forging the smad du byung wa, and excorciates Aro Yeshe Jungney for composed defiled compositions connected to sems sde, etc. The fourteenth century master, Buton accuses Guru Chowang (the treasure revealor of the seven line prayer) of being a fraud, dimisses symbolic dakini script as ridiculous, states outright that Dzogchen teachings are the indepedent fabrications of Nyingmapas. Indeed this was the standard attitude towards Dzogchen, etc. for centuries in Tibet. This is actually at the root of the whole Shugden controversy.
To make it worse, the Nyingmapas, eventually cowed by this pressure to conform to the Sutrayāna gradualism politically enforced by King Trisong Detsen after the outcome of the three year exchange of letters called "the Samye debate", gradually began to present Dzogchen as the summit of a gradual path, abandoning the earliest presentation of Dzogchen as a independent vehicle. There are some people enamored of scholars like Sam Van Schaik, a Sakyapa, who specializes in Dunhuang material. Now, he is a good scholar, and I like very much his point of view. But in my opinion, he has completely misunderstood the intent of the early Dzogchen tradition in Tibet. He presents Dzogchen based on the man ngag lta ba phreng ba (MTP), attributed to Padmasambhava and widely accepted to be his work even in Gelug. As you know or can find out, the MTP presents Dzogchen as the culimination phase of the creation and completion phase based on the Guhyagarbha tantra. Now there is nothing wrong with this at all. But this is not how Dzogchen is presented either in the Seventeen Tantras, klong sde or sems sde. For example, Nubchen, writing in the late 9th century clearly shows that Dzogchen is not merely a completion stage for Dzogchen in his bsam brtan mig gron [SMG]. he identifies Dzogchen as a cig char system. Not only this, but he defends Chan as being the definitive sutrayāna approach because it too is a cig char system. He says for example:
"Do not seek out a philosophical position [siddhanta], there is also nothing to illustrate, if there is something to illustrate, the non-dual is illustrated to be free from activity, thought, or analysis through an example."
But here on this thread, we have many people voice the opinion, to understand Dzogchen you need madhyamaka either Rang stong or gzhan stong, you need to have the view of dependent origination, etc. All kinds of preconditions but one, the indispensible one.
There is but one thing indispensible for Dzogchen, and that is an introduction from a master. As Nubchen points out this is the critical difference between sutra and tantra. The critical difference between tantra and Dzogchen is whether one's practice is based on the notion of cause and result or not. And that is based on whether or not one has authentically recognized one's own stage so that one is possession of that famous rigpa.
Some people are interested in how we know if our practice is moving ahead. It is easy -- are you more integrated, are you having less problems in life? Is your clarity increasing? Are you a nicer person? I do not mean are you a more "compassionate" person in that syrupy fake Lam rim way. I mean are you a nicer person? A decent, ordinary, normal human being who plays well with others? Or are you still an alienated freak who can't get along with anyone and always demands that everyone around you change in conformity with your own nuerosis, especially your religious neurosis?
How can anyone say incidentally these are merely features of a Buddhist path? Look at all the basket cases in Buddhism. Do we really think we have our shit together more than Hindus, Christians and so on? I don't think so -- incidentally I am not making a claim that people who are interested in Dzogchen necesssarily are more together, I have met a lot of flakes in and out of the community and there are a lot of people who think I am a flake. But most people like me even if they think I shoot my mouth off too much (I do).
Back to the main topic: the notion of a vehicle beyond cause and result, one that does not require accumulations, practice with effort, and so on is very threatening to the gradualist establishment in Tibetan culture. The gradualists really hate the message of Atiyoga. It threatens their grip on feudal power. This is why Dzogchen will not be found in Tibetan monasteries and large Dharma centers. It will only be found at the feet of Dzogchen masters. You can take a hundred high Dzogchen empowerments but if you do not understand the main point, then it is of limited benefit. But if you can put yourself at the feet of qualified master who teaches Dzogchen from their own experience then there is no limit of benefit and you will receive transmission whether you are a Buddhist, an Catholic or an Alien. Transmission is beyond mind. Dzogchen is beyond mind, a personal experience beyond reckoning, calculation, something within the reach of everyone who is interested to discover their own nature. So yes, Dzogchen is an aqua regia, a royal water capable of dissolving all limitations whatsoever if one just puts it into sincere practice.
Some people are very attached to the Buddhist clothes in which they find Dzogchen. Those clothes are not so important. Dzogchen texts are relative so they reflect the culture of those they find themselves in. The principle of the three kāyas is beyond language, so it does not matter at all what you call your three kāyas. The three kāyas just express aspects of the wisdom of the basis.
In fact if you closely examine Dzogchen language you see that it uses non-Buddhist examples all the time. For example. the notion of the peacock feather's colors being naturally formed is actually drawn from the Carvaka India materalist school -- they use that example to prove there is no creator, and so do we. A peacocks feather has eyes just because it is the nature of a peacock's feather to have eyes. Wisdom exists in the heart of each and every sentient beings just because it is the nature of a sentient being to have wisdom in each and everyone's heart. We don't have to do anything to create that wisdom. We don't have to do anything at all to develop that wisdom. We cannot improve that wisdom or harm it in anyway. It is as integral to our state as the five elements from which we are made (since they are made from it, anyway).
If we want to understand emptiness in Dzogchen, we do not need to engage in any analysis at all -- we need to merely reflect on the examples of illusion -- that is sufficient for understanding everything is unreal -- no analysis required, no fancy Madyamaka analysis, we don't even have to use the word "emptiness", "Life is but a dream...." In this way we penetrate to the real essence of the teachings.
And then we rest in our own state, or we discover it. These are the only choices we have in Dzogchen, discover, then rest.