Hume mentions most of the secondary characters only once or twice to demonstrate a point. Cicero, however, stands out as someone who's been pretty influential for Hume. Hume calls on Cicero for backup throughout the enquiry, and it's no wonder: this guy was a total brainbox and major figure back in the glory days of Rome. As a successful philosopher, lawyer, and public speaker, his name carries a lot of street cred. Check out some of his memorable quotes here (you'll be surprised how many you've heard before).