> A friend of mine had a squabble with her grammar professor
I'm not surprised. 'Grammar', in the ordinary sense, is a non-subject with no foundation in reality.
> Is a past participle a verb or an adjective in the passive?
It's kind of a silly question, and reveals a certain lack of understanding about how the English verb system works. But the short answer is 'both'. The past participle is an inflected form of words that are lexically verbs, thus the PP is a verb form; but there are contexts where it can function as an adjective. The adjectival use is ancestral to the compound tenses (have gone etc.) but there is no meaningful sense in which the PP could be said to have an adjectival function in those tenses these days. But then you couldn't really say that 'gone' is the verb either; it would be more accurate to say that 'to go' is the verb, and 'would have gone' is the specific inflected/constructed form it takes indicating a particular tense and mood.
Recall The Grammarian's Funeral --
So, with the throttling hands of death at strife, Ground he at grammar; Still, thro' the rattle, parts of speech were rife: While he could stammer He settled Hoti's business -- let it be! -- Properly based Oun-- Gave us the doctrine of the enclitic De, Dead from the waist down.
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Michael J. Smith mjs at smithbowen.net
http://stopmebeforeivoteagain.org http://www.cars-suck.org http://fakesprogress.blogspot.com