In Part II of Fahrenheit 451, Faber calls himself a coward because of his inaction when book-burning was introduced into his society, as he explains to Montag:
"I saw the way things were going, a long time back. I said nothing."
At that time, Faber worked as a college professor and realised that society was undergoing a significant change when only one student signed up for his course, "Drama from Aeschylus to O'Neill." For Faber, this signalled the beginning of a worrying trend in which education and learning were sidelined in favour of entertainment.
To prove his "terrible cowardice," Faber gives Montag one of his creations: a listening device, similar to a Seashell radio, which provides two-way communication. Faber invented this device at home when he locked himself away from the world like a "Queen bee, safe in the hive." Montag and Faber use this device as a means of deflecting Beatty's pro-censorship propaganda. Faber's cowardice, therefore, is what enables the two men to rebel and bring down the fireman system.