Nonetheless, Vajrayana was propagated in Tibet and the lineage of Tibetan Vajrayana kept intact and pure. As Vajrayana places great emphasis on pure lineage, requirement for oral transmission is absolute in order to stamp out false teachings. For the same reason, many strange terms are used deliberately in the Vajrayana texts so that only realized vajra masters can explain what they mean. Another feature of Tibetan Buddhism is to clarify questions through debate; any viewpoint, even just a sentence, can be traced back to its origin in these debates until finally it is proven the bona fide words of the Buddha. Thus, the doctrine of Tibetan Vajrayana is totally reliable.

It seems that the Inner Tantra is not found in the esoteric Buddhism of either Tang Dynasty or Japan but in Tibet only. So I think only authentic practitioners from Tibet really understand what the Inner Tantra is about; they are the real authority on this subject. Other than this group, no one else is qualified to define what Vajrayana is, no matter how grand a title one carries.

- Quote from Gateway to the Vajrayana Path, "The Parable of a Black Snake"