Plutarch, Life of Lycurgus
27.3-4 (tr. Bernadotte Perrin):
Nay more, he actually drove away from the city the multitudes which streamed in there for no useful purpose, not because he feared they might become imitators of his form of government and learn useful lessons in virtue, as Thucydides [2.39.1] says, but rather that they might not become in any wise teachers of evil. For along with strange people, strange doctrines must come in; and novel doctrines bring novel decisions, from which there must arise many feelings and resolutions which destroy the harmony of the existing political order. Therefore he thought it more necessary to keep bad manners and customs from invading and filling the city than it was to keep out infectious diseases.
ἀλλὰ καὶ τοὺς ἀθροιζομένους ἐπ᾽ οὐδενὶ χρησίμῳ καὶ παρεισρέοντας εἰς τὴν πόλιν ἀπήλαυνεν, οὐχ, ὡς Θουκυδίδης φησί, δεδιὼς μὴ τῆς πολιτείας μιμηταὶ γένωνται καὶ πρὸς ἀρετήν τι χρήσιμον ἐκμάθωσιν, ἀλλὰ μᾶλλον ὅπως μὴ διδάσκαλοι κακοῦ τινος ὑπάρξωσιν. ἅμα γάρ ξένοις σώμασιν ἀνάγκη λόγους ἐπεισιέναι ξένους· λόγοι δὲ καινοὶ κρίσεις καινὰς ἐπιφέρουσιν. ἐξ ὧν ἀνάγκη πάθη πολλὰ φύεσθαι καὶ προαιρέσεις ἀπᾳδούσας πρὸς τὴν καθεστῶσαν πολιτείαν, ὥσπερ ἁρμονίαν. διὸ μᾶλλον ᾤετο χρῆναι φυλάττειν τὴν πόλιν ὅπως ἠθῶν οὐκ ἀναπλησθήσεται πονηρῶν ἢ σωμάτων νοσερῶν ἔξωθεν ἐπεισιόντων.
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