I have not been able to find a corresponding Greek (Polytonic) translation or quotation for the Latin phrase In medio stat virtus. I’m pretty sure this translates as: Virtues stands in the middle. However, I took this to be an idea spoken by (and attributed in various places) to Aristotle and his work in Nicomachean ethics and the “golden mean” - the mean being not necessarily the middle, but between 2 (or more) vices.
Does anyone know of a Greek translation of this?
Aristotele, Nicomachean ethics, B6, 14-16
… τῆς δ΄ἀ?ετῆς ἡ μεσότης (?στί)
ἔστιν ἄ?α ἡ ἀ?ετὴ ἕξις π?οαι?ετική, ?ν μεσότητι οὖσα …
Μεσότης δὲ δ?ο κακιῶν…
And also: as before, B6, 13
Μεσότης τις ἄ?α ?στὶν ἡ ἀ?ετή, στοχαστική γε οὗσα τοῦ μέσου.
And in my words:
ἀ?ετὴ ?ν μεσότητι κεῖται
Virtue is put in the middle (that is, between extremes, e.g. hate and love)
Hmmm, any idea how I could write it as “Virtue is in the mean” (as in the golden mean)?
Isn’t that exactly what he meant?
I think I’ve once heard the expression with the addition of χ?υσῆ, but I can’t be sure whether I’m mixing up the latin expression mediocritas aurea or whether it’s a modern neo-greek expression.
And yes, ‘mean’ is probably the better word that did not come to my mind.
Thinking of this i had a flash 
Perhaps you can use the expression
μέτ?ον ἄ?ιστον
This was a “traditional” saying having also some variants, like:
μέτ?ον το ἄ?ιστον
μέτ?ον ἄ?ιστόν ?στι
etc.
Swth/r - thank you for your inputs here; very helpful! But as Bert suggested, there is both a mathematical expression and a philosophical one that use the term Golden Mean. Also, the expressions for moderation (μέτ?ον ἄ?ιστον) are helpful as well.
Thanks all else for comments!