Ὁ κυριεύων λόγος ἀπὸ τοιούτων τινῶν ἀφορμῶν ἠρωτῆσθαι φαίνεται: κοινῆς γὰρ οὔσης μάχης τοῖς τρισὶ τούτοις πρὸς ἄλληλα,

τῷ [τὸ] πᾶν παρεληλυθὸς ἀληθὲς ἀναγκαῖον εἶναι
καὶ τῷ [ἀ]δυνατῷ ἀδύνατον μὴ ἀκολουθεῖν
καὶ τῷ [*? δυνατὸν εἶναι ὃ οὔτ᾽ ἔστιν ἀληθὲς οὔτ᾽ ἔσται,

συνιδὼν τὴν μάχην ταύτην ὁ Διόδωρος τῇ τῶν πρώτων δυεῖν πιθανότητι συνεχρήσατο πρὸς παράστασιν

τοῦ μηδὲν εἶναι δυνατόν, ὃ οὔτ᾽ ἔστιν ἀληθὲς οὔτ᾽ ἔσται.

[2] λοιπὸν ὁ μέν τις ταῦτα τηρήσει τῶν δυεῖν, ὅτι ἔστι τέ τι δυνατόν, ὃ οὔτ᾽ ἔστιν ἀληθὲς οὔτ᾽ ἔσται, καὶ δυνατῷ ἀδύνατον οὐκ ἀκολουθεῖ: οὐ πᾶν δὲ παρεληλυθὸς ἀληθὲς ἀναγκαῖόν ἐστιν, καθάπερ οἱ περὶ Κλεάνθην φέρεσθαι δοκοῦσιν, οἷς ἐπὶ πολὺ συνηγόρησεν Ἀντίπατρος. [3] οἱ δὲ τἆλλα δύο, ὅτι δυνατόν τ᾽ ἐστίν, ὃ οὔτ᾽ ἔστιν ἀληθὲς οὔτ᾽ ἔσται, καὶ πᾶν παρεληλυθὸς ἀληθὲς ἀναγκαῖόν ἐστιν, δυνατῷ δ᾽ ἀδύνατον ἀκολουθεῖ. [4] τὰ τρία δ᾽ ἐκεῖνα τηρῆσαι ἀμήχανον διὰ τὸ κοινὴν εἶναι αὐτῶν μάχην.

The argument called the ruling argument (ὁ κυριεύων λόγος） appears to have been proposed from such principles as these: there is in fact a common contradiction between one another in these three propositions, each two being in contradiction to the third. The propositions are,

that every thing past must of necessity be true;
that an impossibility does not follow a possibility;
and that a thing is possible which neither is nor will be true.

Diodorus observing this contradiction employed the probative force of the first two for the demonstration of this proposition,

That nothing is possible which is not true and never will be.

Now another will hold these two: That something is possible. which is neither true nor ever will be: and That an impossibility does not follow a possibility. But he will not allow that every thing which is past is necessarily true, as the followers of Cleanthes seem to think, and Antipater copiously defended them. But others maintain the other two propositions, That a thing is possible which is neither true nor will be true: and That everything which is past is necessarily true; but then they will maintain that an impossibility can follow a possibility. But it is impossible to maintain these three propositions, because of their common contradiction.
(Discourses, Book 2, chapter 1, "Against those who embrace philosophical opinions only in words," Perseus Project, Tufts

If then any man should ask me, which of these propositions do you maintain? I will answer him, that I do not know; but I have received this story, that Diodorus maintained one opinion, the followers of Panthoides, I think, and Cleanthes maintained another opinion, and those of Chrysippus a third. What then is your opinion? I was not made for this purpose, to examine the appearances that occur to me, and to compare what others say and to form an opinion of my own on the thing. Therefore I differ not at all from the grammarian.