A nation can survive fools, and even the ambitious; but it cannot survive treason from within. An enemy at the gates is less formidable, for he is known and he carries his banners openly; but the traitor moves freely among those within the gate, his sly whispers rustling throughout all the galleys, and is heard in the very hall of the government itself. For the traitor appears not as a traitor – he speaks in the accents familiar to his victims, he wears their face and their garment, and he appeals to the baseness that lies deep in the hearts of all men. He rots the soul of a nation – he works secretely and unknown in the night to undermine the pillars of a city – he infects the body politic so that it can no longer resist. A murderer is less to be feared.
Cicero, 42 B.C.