Laudator Temporis Acti

Isocrates, On the Peace 3 (tr. George Norlin):

I observe, however, that you do not hear with equal favour the speakers who address you, but that, while you give your attention to some, in the case of others you do not even suffer their voice to be heard. And it is not surprising that you do this; for in the past you have formed the habit of driving all the orators from the platform except those who support your desires.

ὁρῶ δ᾿ ὑμᾶς οὐκ ἐξ ἴσου τῶν λεγόντων τὴν ἀκρόασιν ποιουμένους, ἀλλὰ τοῖς μὲν προσέχοντας τὸν νοῦν, τῶν δ᾿ οὐδὲ τὴν φωνὴν ἀνεχομένους. καὶ θαυμαστὸν οὐδὲν ποιεῖτε· καὶ γὰρ τὸν ἄλλον χρόνον εἰώθατε πάντας τοὺς ἄλλους ἐκβάλλειν, πλὴν τοὺς συναγορεύοντας ταῖς ὑμετέραις ἐπιθυμίαις.

Id. 10-11:

And yet, if you really desired to find out what is advantageous to the state, you ought to give your attention more to those who oppose your views than to those who seek to gratify you, knowing well that of the orators who come before you here, those who say what you desire are able to delude you easily—since what is spoken to win favour clouds your vision of what is best—whereas those who advise you without regard to your pleasure can affect you in no such way, since they could not convert you to their way of thinking until they have first made clear what is for your advantage. But, apart from these considerations, how can men wisely pass judgement on the past or take counsel for the future unless they examine and compare the arguments of opposing speakers, themselves giving an unbiased hearing to both sides?

καίτοι προσῆκεν ὑμᾶς, εἴπερ ἠβούλεσθε ζητεῖν τὸ τῇ πόλει συμφέρον, μᾶλλον τοῖς ἐναντιουμένοις ταῖς ὑμετέραις γνώμαις προσέχειν τὸν νοῦν ἢ τοῖς καταχαριζομένοις, εἰδότας ὅτι τῶν ἐνθάδε παριόντων οἱ μὲν ἃ βούλεσθε λέγοντες ῥᾳδίως ἐξαπατᾶν δύνανται (τὸ γὰρ πρὸς χάριν ῥηθὲν ἐπισκοτεῖ τῷ καθορᾶν ὑμᾶς τὸ βέλτιστον), ὑπὸ δὲ τῶν μὴ πρὸς ἡδονὴν συμβουλευόντων οὐδὲν ἂν πάθοιτε τοιοῦτον· οὐ γὰρ ἔστιν ὅπως ἂν μεταπεῖσαι δυνηθεῖεν ὑμᾶς, μὴ φανερὸν τὸ συμφέρον ποιήσαντες. χωρὶς δὲ τούτων πῶς ἂν ἄνθρωποι καλῶς δυνηθεῖεν ἢ κρῖναι περὶ τῶν γεγενημένων ἢ βουλεύσασθαι περὶ τῶν μελλόντων, εἰ μὴ τοὺς μὲν λόγους τοὺς τῶν ἐναντιουμένων παρ᾿ ἀλλήλους ἐξετάζοιεν, αὐτοὶ δ᾿ αὑτοὺς κοινοὺς ἀμφοτέροις ἀκροατὰς παράσχοιεν;

Oops, I see that "echo chamber" is on Lake Superior State University's 42nd Annual List of Banished Words.