Seneca was a Roman Stoic philosopher and statesman. He is best known for his dramatic plays and philosophical works that include some of the most important writings on stoicism. On a Happy Life was written in his later years as a letter to his brother. The main premise in it is that we can only be happy and live a happy life by being reasonable. This age-old wisdom is as applicable to us in our lives today as it was when Seneca wrote it in Imperial Rome.