In his answer to Q: What is the difference in meaning/usage between "nasciturus" and "nascendus"?, Mitomino provided some interesting examples of the use of the gerundive. One of these:
“semel haec (alta) mihi vivenda sint an saepe nascendum?” (Sen. Ep. 65.20) =
“Whether these (heights) ought to be lived by me just once, or must one be born again and again?”
Although Seneca is ostensibly writing to a friend, Lucilius, the quote is part of a soliloquy; Seneca is talking to himself. It ends in a question mark indicating a direct question. The usual sources – Latin Library, Perseus – also give this with a question mark.
A double or alternative question of “whether-or-not” type is usually indirect:
“rogavit utrum [optional] laetus esset an tristis.” =
“He asked whether he was happy or sad.”
Indirect Q.: interrogative with subjunctive, requires no question mark (utrum = “whether” is optional).
If this is a direct Q., then the present (-cum-future) subjunctive sint can only be the part of sum required for a gerundive of obligation: vivenda sint; the dative, mihi, is indicating Seneca, the person upon whom the obligation falls.
Allen & Greenough p. 443:
The subjunctive was used in sentences of interrogative form, at first when the speaker wished information in regard to the will or desire of the person addressed. But such questions when addressed by the speaker to himself, as if asking for his own advice, became a deliberative or not infrequently, merely exclamatory (p. 573).
Woodcock p. 172:
[…] if a jussive subjunctive (a command) is used interrogatively, an inquiry is made as to someone’s will [...] e.g. “maneat” = “Let him stay”; “ubi maneat?” = “Where is he to stay?”
This type of (direct) question, with the verb in the subjunctive, was the start of a wide range of uses in which the subjunctive is called “Deliberative” […] Only in the […] case (first person speaking, spontaneously) is the subjunctive truly “deliberative”.
Soliloquising, indicating hesitation, doubt or helplessness (Plaut. Curc. 589):
“quid ego faciam? maneam an abeam?” =
“What shall I do? Shall I stay or go?”
Woodcock did not contrast the deliberative-subjunctive, direct-question with the indirect equivalent: "quid ego faciam?" (direct);
"quid ego faciam nescio." = "I don't know what I shall do." (indirect).
(A & G) p.575(b): The Deliberative Subjunctive remains unchanged in an indirect question, except sometimes in tense:
"quo me vertam nescio." (Clu. 4) (indirect) = "I do not know which way to turn.";
"quo me vertam?" (direct) = "Which way shall I turn?".
SENECA EPISTLE 65.20:
Seneca was soliloquising: the rest of the epistle is written in a similar vein:
“ego nesciam unde descenderim?” =
“Must I be ignorant of the heights whence I have descended?”
“ego ista non quaerem?” =
“Am I not to ask these questions?”
That Seneca is talking to himself, not Lucilius, is exemplified by the repetition of ego – unusual in Latin speech in which ego is understood in the first-person verb conjugation.
Interesting is an article from Ohio State University, “Subjunctive Questions”, which compares and contrasts the approaches of (A & G) and Woodcock to the deliberative subjunctive. That (A & G) appear to be saying that, for the subject addressing himself, deliberative and exclamatory Qs. must always include a subjunctive; whereas Woodcock p. 172: “In Qs. that are truly deliberative, the indicative is almost as common as the subjunctive.”
Ohio State explains:
[…] deliberation is not a syntactical category; it is a function of context and rhetoric, not grammar. The fact that these eminent grammarians disagree […] indicates that it [deliberation] is a phantom elephant and these grammarians have merely found different parts of it.
Is the (“semel haec […]”) quote from Seneca a direct or indirect question?