The phrase quid si (hundreds of examples) was not at all unheard of.
It works for both possible and impossible conditionals, and impossibility is best expressed by choosing perfect or pluperfect conjunctive.
This is what Cicero would do, too.
An artificial example:
What if he were in Rome now?
Quid si ille Romae nunc esset?
Here's an example from Cicero, Academica 1.24 (it even uses the preposition sine). The general parallelism of the ideas introduced by neque...neque makes it clear that the prepositional phrase is equivalent to or encapsulates an 'if' clause:
de natura autem (id enim sequebatur) ita dicebant ut eam dividerent in res duas, ut altera esset efficiens, altera ...
It doesn't make any sense because it's not a Latin construction. The Latin appears to be a translation of the Greek:
εἰ ἔσται τὰ ἔτη ταῦτα δρόσος καὶ ὑετὸς ὅτι εἰ μὴ διὰ στόματος λόγου μου.
This is in turn is a rather literal "translation" of the Hebrew:
אִם־יִהְיֶה הַשָּׁנִים הָאֵלֶּה טַל וּמָטָר כִּי אִם־לְפִי דְבָרִי
You'll notice the parallel ...
Yes, the construction is the same whether the relative is modifying a noun (relative adjective) or not (relative pronoun). The latter type is more frequent, but there are examples of the former, e.g. this from Smyth:
ὥστ᾽ ἀποφύγοις ἂν ἥντιν᾽ ἂν βούλῃ δίκην
"so that you can get off in any suit you please” (Ar. Nub. 1151)
I found this in an online version of Plater & White's A grammar of the Vulgate:
In emphatic speech, especially in adjurations, si = a negative
Here are some of the attestations:
'semel iuraui in sancto meo, si Dauid mentiar' (=I will not lie unto David) Ps. 89. 34 (88. 36), 'si introibunt in requiem meam' (= they shall not enter into my rest)
The first example that came to my mind was, VG Ioh 15:5:
Sine me nihil potestis facere / without me you can do nothing
It is put by John in the mouth of Jesus preaching. This, of course, does not meet the Classical requirement...
But then I started searching for sine+nihil, restricting the search to something concrete...
Google gave a number of ...
It's still a present general conditional. You might have noticed in some grammars that they will say for the present general apodosis, it takes the "present indicative or an equivalent." The aorist is the equivalent here, and functions as a gnomic aorist.
See Smyth § 2338:
The gnomic aorist is equivalent to the present indicative in apodosis.
There are a couple issues to sort out.
First, the past tense of certain verbs such as debeo, possum, oportet, etc., can carry counterfactual force, even when in the indicative. This can occur in independent clauses with no expressed protasis.
Bonus vátes poteras esse, nam quae sunt futura dicis. (Plautus,
You would have made a good ...
So what's going on here is that 19th century Latin textbooks never caught up with the 20th century. Toss all the "would/should" nonsense. That's not how we talk anymore. Here's how we would translate these things today:
Present (potential) subjunctive:
Si Marcus Iuliam amet, ea eum amet.
If Marcus were to love Julia [which is one of the options ...
This is conditional sentence, and 'si' is the sign of the conditional here; 'Si', (if) with 'nisi' (unless) , the negative ni- refers to the principal clause, which is thus denied, if the conditional clause is accepted; (Gildersleeve & Lodge)
There is also said, the negative of 'si' is 'si non' or 'nisi'.
Mind there are no similar examples given so it ...
Here is a potentially similar example of a past dilemma from Diogenes Laertius (3rd c. AD), Vitae Philosophorum, in which he uses the aorist optative for the protasis. The surrounding clause is in direct speech, so the apodosis is in an aorist infinitive. The OP is probably in a better position to judge whether this fits the case or not.
φησὶ δὲ Δημήτριος ...
For the butter example, I think a future more vivid is probably the way to go, since it's explaining the logical facts of the case and is as direct as direct can be. Cf. Cato's si me rogabis, sic dicam, "if you ask me, I will say the following." Future + future indicative is fine.
The future perfect would be used when the action in the protasis &...
If you continue to look into the abyss then when does the abyss take its turn to look into you? Do you stand there forever; or, until you starve to death or just fall asleep? By definition, at some point, you stop gazing. At this juncture does the abyss decide to commence his/ its vigil of yourself?
A conditional (simple conditions) sentence using future-...
I found this statement in an Oxford Latin Syntax Volume I, 11.137 "the anaphoric pronoun is":
For the anaphoric pronoun a distinction must be made between the oblique forms and the nominative subject...
Without ripping too much from the book, it effectively states that no subject is preferred if the subject is well-introduced, while if the well-...
It possible to read the sentence with fueris having a perfect meaning: "… as if you had dined with me."
I read the idea roughly like "I have accepted you as a guest in my house in the past, and therefore my home is yours".
Convictor can mean someone who lives together, but also "table companion" and "familiar friend" are suggested in L&S.