Context: My difficulty is the first word in the sentence under study, qua. I can’t provide a grammatical rationale for it, and I can’t find a way to look it up. Here Augustine continues to attack the pagan ideas about daemones. Augustine interrupts a previous discussion of angels, in order to renew his focus on the daemones. Just above, Augustine has declared that God and the angels do not experience passions such as anger.
Qua interim de sanctis angelis quaestione dilata videamus quem ad modum dicant Platonici medios daemones inter deos et homines constitutos istis passionum aestibus fluctuare.
Translation: With this question of the holy angels laid aside for a while, let’s examine the platonists’ teaching on the daemones, who, located between humans and the celestial gods [so the platonists say], toss about on the waves of those passions [ that do not shake the angels].
I have always had trouble with qua, and with other such words, but I can never find a helpful dictionary entry or a reference in A&G for this use.
You correctly recognized this as an ablative absolute. Qua here is the relative adjective used as a connective with what precedes, instead of a demonstrative hac.
A&G 308f:
f. A relative pronoun (or adverb) often stands at the beginning of an independent sentence or clause, serving to connect it with the sentence or clause that precedes:—
“Caesar statuit exspectandam classem; quae ubi convēnit ” (B. G. 3.14) , Cæsar decided that he must wait for the fleet; and when this had come together, etc.
quae quī audiēbant, and those who heard this (which things).
quae cum ita sint, and since this is so.
“ quōrum quod simile factum ” (Cat. 4.13) , what deed of theirs like this?
quō cum vēnisset, and when he had come there (whither when he had come).
[*] Note.–This arrangement is common even when another relative or an interrogative follows. The relative may usually be translated by an English demonstrative, with or without and.
I think quem ad modum is simply “how” rather than “the extent to which.” (Like quo modo, it’s often written as a single word.)
And Hugh, “those waves of passions” rather than “the waves of those passions.”
But you’ve understood the passage all right. Perhaps it was the noun with qua that threw you off (so that the relative functions as an adjective rather than a pronoun). Lit. “Which question meanwhile having been laid aside” (abl.abs.) i.e. “With this question …” just as you have it.