Which reading does the monster say introduced him to idea of men as both powerful and virtuous yet vicious immoral?

The monster in Mary Shelley's *Frankenstein* says it was Plutarch's *Lives* that introduced him to the idea of men being both powerful and virtuous yet vicious and immoral.

He describes how the book revealed to him the "wretchedness" of humanity, showcasing both their "noble" and "benevolent" qualities as well as their "cruelty" and "depravity."