§12.25g.1ὅτι οὔτε περὶ τῶν κατὰ πόλεμον συμβαινόντων δυνατόν ἐστι γράψαι καλῶς τὸν μηδεμίαν ἐμπειρίαν ἔχοντα τῶν πολεμικῶν ἔργων οὔτε περὶ τῶν ἐν ταῖς πολιτείαις τὸν μὴ πεπειραμένον τῶν τοιούτων πράξεων καὶ περιστάσεων.
Indeed, it is impossible for one who has no experience of military operations to write well about what happens in war, or for one who is unversed in such actions and circumstances to write well about what happens in political affairs.
§12.25g.2λοιπὸν οὔτʼ ἐμπείρως ὑπὸ τῶν βυβλιακῶν οὔτʼ ἐμφαντικῶς οὐδενὸς γραφομένου συμβαίνει τὴν πραγματείαν ἄπρακτον γίνεσθαι τοῖς ἐντυγχάνουσιν·
Consequently, with nothing being written by bookish writers either with practical knowledge or with vividness, it happens that their treatise becomes useless to those who read it.
εἰ γὰρ ἐκ τῆς ἱστορίας ἐξέλοι τις τὸ δυνάμενον ὠφελεῖν ἡμᾶς, τὸ λοιπὸν αὐτῆς ἄζηλον καὶ ἀνωφελὲς γίνεται παντελῶς.
For if one were to take away from history what is capable of benefiting us, the remainder of it becomes completely unattractive and useless.
§12.25g.3ἔτι δὲ περὶ τῶν πόλεων καὶ τόπων ὅταν ἐπιβάλωνται γράφειν τὰ κατὰ μέρος, ὄντες ἀτριβεῖς τῆς τοιαύτης ἐμπειρίας, δῆλον ὡς ἀνάγκη συμβαίνειν τὸ παραπλήσιον, καὶ πολλὰ μὲν ἀξιόλογα παραλείπειν, περὶ πολλῶν δὲ ποιεῖσθαι πολὺν λόγον οὐκ ἀξίων ὄντων·
Moreover, when they undertake to write about cities and places in detail, being unpracticed in such experience, it is clear that the same result must happen: they omit many noteworthy things, while making a long discourse about many things that are not worth it.
ὃ δὴ συμβαίνει μάλιστα Τιμαίῳ διὰ τὴν ἀορασίαν.
This is precisely what happens most of all to Timaeus because of his lack of personal observation.