General James Mattis is part of a long line of tradition of Stoic warriors. Just as Frederick the Great carried the Stoics in his saddlebags as he led his troops, or Cato proved his Stoicism by how he led his own troops in Rome’s Civil War, Mattis has long been known for taking Marcus Aurelius’ Meditations with him on campaign. “Reading is an honor and a gift,” he explains, “from a warrior or a historian who—a decade or a thousand decades ago—set aside time to write.” Yet many people spurn this gift and still consider themselves educated. “If you haven’t read hundreds of books,” Mattis says, “you’re functionally illiterate.” Channeling Marcus Aurelius, Mattis notes that human beings have been fighting and dying and struggling and doing the same things for eons. To not avail yourself of that knowledge is profoundly arrogant and stupid. To fill up body bags of young soldiers while a commander learns by experience? It’s worse than arrogant. It’s unethical, even murderous. Well, the same is true for much less lethal professions. How dare you waste your investor’s money by not reading and learning from the mistakes of other entrepreneurs? How dare you so take your marriage or your children for granted that you think you can afford to figure this out by doing the wrong things first? What is the upside of trying to make it in the NFL all on your own, and not looking for shortcuts and lessons from seasoned pros and students of the game who have published books? There is no real job training for an emperor or the advisor to the emperor, but you can imagine both Marcus Aurelius and Seneca read heavily from and about their predecessors. The stakes were too high for them not to. In Mattis’ view, no Marine, and no leader, is excused from studying. Consider yourself assigned to this as well. It’s wonderful that you’re reading this email, but more is demanded of you. Drink deeply from history, from philosophy, from the books of journalists and the memoirs of geniuses. Study the cautionary tales and the screw ups, read about failures and successes. Read constantly—read as a practice.Because if you don’t, it’s a dereliction of duty.