Thanks so much everyone for the help. Nate, perhaps my use of (probably British!) terminology was confusing. All my grammar books (Morwood Oxford and Anderson & Taylor BCP) divide conditionals up into two general categories: real and unreal. By "unreal" they mean anything that is less likely to happen, whether it is hypothetical (If X were to happen, Y would happen) or completely closed (If X had happened, Y would have happened). They also treat ἐαν/ἀν/ἠν + subjunctive protasis followed by apodosis in present not as a "general real conditional" like Goodwin and Smythe but as an indefinite temporal clause - ἐαν τις κλεπῃ, κολαζεται, "If anyone (ever) steals, he is punished" could equally be translated "Whenever anyone steals, he is punished"; likewise the past equivalent εἰ + optative (If anyone ever did X...) followed by imperfect is treated as an indefinite in the past. At any rate obviously neither of these "semi-conditionals" are what Plato has in mind here. So in this sense the only use of an optative in the protasis of conditions is, as far as I am aware, in a future unreal or less vivid or whatever you want to call it (If X were to happen
, Y would happen). That's why your brilliant explanations about it being in effect oratio obliqua must surely be right
? The original thought in his mind was something like "I will be purified from guilt if, after all, perhaps the dream figures are enjoining me to compose this sort of art/music" which when being related to us is all put into the optative. Surely, Bartholomew, it is not the ἐπιτάττοι which of itself is the reason why it is in the optative (that the dream figures presumably spoke to him to do it), but the indirect statement is implicit in the εἰ ἄρα? This seems similar to Latin where quod, which usually takes the indicative, may suddenly spring into the subjunctive since it is only the alleged reason of the speaker. Anyways, thanks for all the help again - if after all perhaps it seems to make sense
P.S. This use of implied indirect statement I guess interestingly means that the optative does in fact work in terms of tense rather than aspect, since in its use in indirect statements it works in this way. So if Plato had used the aorist optative here, then that would have implied that Socrates' deliberation in the past was about the then past and so would be translated with a pluperfect: "If after all perhaps it had enjoined me to...".
hic Graeca doctrina ore tenus exercitus animum bonis artibus non induerat.