My last post should have been sufficient to neutralize arguments that the Tebtunis priests’ engagement with Greek was driven by administrative requirements, by the demands of the State. (This has been argued by, e.g., Fowden, The Egyptian Hermes, Cambridge 1986, p. 16). The question of language preference, however, is another, more complicated, matter, in part because the response of the priests was no doubt individualized. Still, there was no other group in Roman Egypt better situated to “choose” Egyptian, at least in the realm of writing; the “rarefied” Egyptian scripts were beyond everyone else. And so it might seem completely predictable to find late demotic letters (e.g.) among the documents from the crocodile temple. But the interpretation of the texts in question is not so straightforward (cf. my comments in G. Bastianini & A. Casanova, eds., 100 anni di istituzioni fiorentine per la papirologia, p. 77), and I would suggest that for at least some priests (and not excluding those highest in the temple hierarchy), Greek was the language of preference.
The spark for this hypothesis was an ineditum in the Berkeley collection, a (possibly autograph) letter from the prophetess Isidora to her husband, the diadochos propheteias Kronion. This document is written in Greek, and in communication between a wife and husband of the same ethnic background, I would expect language selection to reflect the preference of the participants, though one can of course conceive scenarios in which the discourse or its circumstances were determinative (e.g., if we decide to argue that the letter is not an autograph, and assume that an Egyptian-language scribe was unavailable). In any case, the hypothesis spurs reconsideration of some chestnuts, e.g., the extent to which the shift from demotic to Greek oracle questions under the Romans was driven by priestly preference, as opposed to the oft-cited needs of the populace. Or the extent to which translations of Egyptian texts, like the Greek version of the Myth of the Sun’s Eye or the Oxyrhynchite Book of the Temple, reflect priestly requirements and interests (cf. also the creation of “Old Coptic”), as opposed to demands from Greek outsiders.