It's an in-depth analysis of Prajnaparamita texts, the various Dasabhumi schemas in the Mahayana canon, some look at Pali texts, etc. in order to discern what is meant by the "ground of non-retrogression." Here are some of my notes...
- Irreversibility is used in a few different ways in different texts
The Irreversibility of the Sravakayana texts refers to not backsliding from the path in general
The irreversibility of the Mahayana texts refers to not falling into the fates of the arhat or the pratyekabuddha, these are two different Sanskrit words (which I don't recall precisely right now)
The Astasahasrika PPJ references at least two different dasabhumi schemas (where arhatship == bhumi 7) as well as the pancamarga schema (which is determined to be on the late side)
There appear to be six different dasabhumi schemas found in the Mahayana canon, two of which appear in the Avatamsaka.. The Dasabhumika Sutra/Chapter became the standard model, but another character has arhatship/extinction of the outflows at bhumi 7, in line with the PPJ texts
Most discussions of irreversibility are about how to avoid becoming an arhat, NOT about how to avoid dropping down the path
The first bhumi is considered entering the gotra of bodhisattvas, so you will never fall from the path at this point
It is apparently possible to drop down in bhumis before the 7th/8th, but never lower than the first once it's attained (this is a big one, I think)
The pancamarga system seems to have begun development in the 1st century BCE, along with rudimentary dasabhumi schemas, and it wasn't until the Abhilam.... I forget the spelling, that Maitreya text that doesn't exist in Chinese, it wasn't until that when the bhumis and pancamarga were attempted to correlate to one another
It was not until Je Tsongkhapa that the concept of complete irreversibility (tantamount to 8th bhumi in the conventional bhumi schema) was accorded to the first bhumi, with him declaring that they were irreversible bodhisattvas, but simply have not manifested the marks of an irreversible bodhisattva yet
prediction in the presence of a living Buddha was not a definitive sign of irreversibility in the technical sense, but in a "the Buddha knows all sense", insofar as a bodhisattva can just happen to be alive during the time of a Buddha and get a prediction even at the first bhumi, and can still backslide after this point
meditative methods to determine if one had received a prediction in the past is only sufficient to infer a prediction, because the methods only reveal the signs of an irreversible bodhisattva (i.e. all irreversible bodhisattvas have received predictions, therefore, if one receives signs of irreversibility, there must have been a previous prediction)
The bodhisattva career being split into two distinct phases, with the first phase being exactly the same as the path of the sravakas, is confirmed in the APPJ (prior to this, I was simply extrapolating that understanding from the Yogacarabhumisastra, but it's nice to see that it's clearly spelled out somewhere, and is spelled out in the earliest Mahayana text known)