As a young boy, the famed basketball coach George Raveling learned an invaluable lesson from his grandmother, who raised him. As they were preparing dinner in the kitchen one evening she began to tell him about how in the days of slavery, the plantation owners would hide their money in books on the shelves of their libraries. “Why did the slave masters hide their money in books, George?” she asked him.

“I don’t know Grandma,” George replied, “why did they do that?”

“Because they knew the slaves couldn’t read,” she said, “so they would never take the books down.”

It is worth pointing out today that money is still hidden in the pages of books—though not because someone put it there in order to keep it from you. Think of someone like Warren Buffett—one of the richest men in the world. Do you know what he traces his fortune back to? His single best investment decision? It’s a book. The Intelligent Investor by Benjamin Graham, which he first read at the age of 19. “I can’t remember what I paid for that first copy,” he explained in his 2013 letter to shareholders, but “of all the investments I ever made…[it] was the best.” In the 1940s, books would have cost perhaps a dollar but even if Buffett had paid billions for it, it’d have been a pretty good ROI.

Epictetus found freedom from slavery, long before he was legally free. How? In the writings of the Stoics, in the words of Musonius Rufus. He read his way to freedom, literally and figuratively, as Frederick Douglass would do in America two thousand years later.

We read because it makes us powerful. When we don’t read, we are weaker—easier to control, less than what we are capable of being. That’s why slaveowners weren’t content to just hope their slaves stayed ignored. They made it illegal to teach them to read.

Never forget that it’s in your self-interest to read—there’s incredible power and money in it.