The Closed Society and Its Enemies

"And this was the reason why he forbade them to travel abroad, and go about acquainting themselves with foreign rules of morality, the habits of ill-educated people, and different views of government. Withal he banished from Lacedaemon all strangers who would not give a very good reason for their coming thither; not because he was afraid lest they should inform themselves of and imitate his manner of government (as Thucydides says), or learn anything to their good; but rather lest they should introduce something contrary to good manners. With strange people, strange words must be admitted; these novelties produce novelties in thought; and on these follow views and feelings whose discordant character destroys the harmony of the state. He was as careful to save his city from the infection of foreign bad habits, as men usually are to prevent the introduction of a pestilence." - Plutarch, Life of Lycurgus