A terma is, roughly, a “revelation.” As in most Nyingma lineages, the Aro teachings are based mainly on a terma: the Aro gTér. (gTér is an unusual spelling of “terma”. The g is silent, so it is pronounced “aro ter,” rhyming with “hair.” Sometimes you also see “Aroter.”)
The person who discovers a terma is called a terton. Aro Lingma (illustrated above) was the terton of the Aro gTer.
In Tibet, wealth, power, fame, and women were often showered on tertons. So, for the clever, it was often tempting to invent some plausible-sounding religious nonsense and call it a terma. And so there was a serious problem of knowing which terma were genuine revelations, and which were well-crafted fakes.
It would be convenient if there were a good way to test terma, or a central authority that could put its stamp of approval on the real ones. Unfortunately, there isn’t. This is a problem for anyone who wishes to follow any Nyingma lineage. As an alternative, one could join a Tibetan School that isn’t based on terma. That might seem safer. However, those lineages are based on other scriptures that are also rejected by almost all Buddhists outside Tibet. So it doesn’t really help. There are no uncontroversial branches of Buddhism. There is no safety in Buddhism.
The next several pages of this site are devoted to the question “Is the Aro gTer valid?” The answer depends partly on “according to what standard?”
There are several standards according to which the answer is “obviously not.” For example, from point of view of Islam, the Aro gTer is definitely invalid. But so is the rest of Buddhism, so that is not interesting. Similarly, some Tibetans reject all terma. However, most accept at least some.
The most reasonable standard is that of the Nyingma tradition. The Aro lineage belongs to that tradition. I will explain the Nyingma theory of terma validation. Unfortunately, it turns out to be less helpful than we would like. It cannot give a definitive, yes/no answer.
Another reasonable standard is that of comparative scholarship. That perspective cannot answer the question “is the Aro gTer magically effective.” However, it can answer the question “is the Aro gTer consistent with broadly-accepted Nyingma texts.” The answer, in short, is “yes.”
By the way, it is important to separate two questions that have sometimes been run together: “Is the terma valid?” and “Is the lineage history true?” Either could be valid without the other, or both or neither might be. The Aro gTer makes almost no reference to its history. I’ll discuss the lineage history elsewhere.
Given that it is impossible to reliably authenticate termas in theory, what have Tibetans done in practice? The answer is disappointing and unhelpful.
So, finally, I ask, what should we do, as Westerners approaching lineages based on terma?