This essay, addressed to Seneca's brother Gallio, explores what constitutes true happiness. Written around 58 CE, it defends the Stoic position that happiness lies in virtue, not pleasure, while responding to critics who accused Seneca of hypocrisy for his own wealth.
The essay distinguishes between pleasure and joy, arguing that genuine contentment comes from living in agreement with nature and reason.
"The happy life, therefore, is a life that is in harmony with its own nature."
— On the Happy Life, 3