PUL was creative in his interpretations of Irish grammar, partly because he didn’t believe in trying to squeeze Irish into the straitjacket of Latin grammar (or English grammar). He would often insist that native speakers knew instinctively that the standard grammatical explanations were false. Take this for example (from a letter to Gearóid Ó Nualláin), about the neuter pronoun ea:
The ‘scholars’ made up their minds comfortably that it is the neuter pronoun. They said―Latin is, ea, id, Irish é, í, ea, and they were delighted. I knew by instinct that they were entirely wrong. I had before my mind fixed for a length of time the question: ‘what is this ea?’ I was going over in my mind all the constructions in which ea is used. The result is that I have been driven to the conclusion that ea is not a pronoun at all, that it is a substantive, and that it represents the truth of some statement like the English word ‘fact.’ I have been driven to it by long and close thinking, while keeping rigidly before my mind the fact that the Irish speech was built up ages before any of the present European speeches were built and in accordance with building rules of which people have not the faintest shadow of an idea. Look: an fear é? Is ea [a fact]. An é an fear é? Is é [a pronoun]. I was at it for a long time, until at last the ea became in my mind a ‘fact’ or a ‘truth,’ or an existing combination of facts or of truths or of circumstances or of modes of being. The English expression ‘that’s a fact’ is like it.”
Gearóid Ó Nualláin comments to the effect that PUL was clearly wrong on this, and that ea is the neuter pronoun. By derivation, it is the neuter pronoun, but I am wondering whether PUL’s explanation might be a better fit with the grammar of Irish as it came to be in the modern period, despite the etymological derivation? His explanation might be a simpler way of teaching the matter to students of Irish.