Ryan Holiday has written several self-help books, including Perennial Seller, The Lives of the Stoics, The Daily Dad, and The Daily Stoic, many of which explore messages and themes from Stoic thought. His book Ego Is the Enemy forms part of an informal series that includes his previous work, The Obstacle is the Way, and his later additions, Courage Is Calling, Stillness Is the Key, and Discipline Is Destiny. Taken together, these works communicate a host of Stoic principles using Holiday’s favored approach of real-life anecdotes from ancient and modern history.

Stoicism is an ancient Greco-Roman philosophy. The first Stoic school of philosophy was founded by Zeno around 300 BCE, but the philosophy reached its height in the first and second centuries CE under the Roman Empire. The Roman orator and politician Cicero (106 BCE-43 BCE) is often credited with first popularizing the main tenets of the philosophy in Rome. The most famous Stoic philosophers recognized today are Epictetus (50 CE-135 CE), Seneca the Younger (4 BCE-65 CE), and the emperor Marcus Aurelius (121 CE-180 CE). Epictetus’s teachings were collected and circulated by one of his pupils and later published as Discourses and Enchiridion. Seneca became famous for both his tragedies and his philosophical works, including On the Brevity of Life and Letters from a Stoic.