In general, gladiators were condemned criminals, prisoners of war, or slaves bought for the purpose of gladiatorial combat by a lanista, or owner of gladiators. Professional gladiators were free men who volunteered to participate in the games. In The Satyricon, Petronius suggested that Roman crowds preferred combat by free men over that of slaves. For example, the character of Echion is excited about games in which free men, "not a slave in the batch," will fight. Though low on the social scale, free men often found popularity and patronage of wealthy Roman citizens by becoming gladiators. The emperor Augustus sought to preserve the pietas and virtus of the knight class and Roman senate by forbidding them to participate in gladiatorial combat. Later, Caligula and Nero would order both groups to participate in the games.