Cicero's real argument in the Catilinarian Orations (63 BC) is that the concealed enemy is more dangerous than the avowed one. An open foe can be met at the walls; a hidden traitor among citizens infects the state from within, like a disease in the body, and cannot be countered because the state cannot see it. He makes the contrast explicit: Catiline, once he fled, became less threatening precisely because "there is a wall between us," while those who "dissemble their enmity" and remain in the Senate are the true peril. The widely circulated quote — "A nation can survive its fools, and even the ambitious. But it cannot survive treason from within. The enemy can be destroyed but the enemy within can be difficult to detect.