The Stoics taught Cato that there were no shades of gray. There was no more-or-less good, no more-or-less bad. Whether you were a foot underwater or a fathom, you were still drowning. All virtues were one and the same virtue, all vices the same vice.

It is the kind of austere scheme that seems unreasonable to live by and almost entirely impossible for the flux of war and politics. But Cato made it work. He refused political compromise in every form, to the point that bribe-takers turned his name into an aphorism: “What do you expect of us? We can’t all be Catos.”

He demanded the same of his friends, his family, and his soldiers. He was infuriating to his enemies, and he could seem crazy to his allies. And yes, sometimes he took his adherence to principle down absurd, blind alleys. But he also built an impossible, almost inhuman standard that brought him unshakable authority. By default, he became Rome’s arbiter of right and wrong. When Cato spoke, people sat up straighter. When he was carted off to jail by Julius Caesar, the entire Senate joined him in sympathy, forcing Caesar to let Cato go.

Many in Cato’s day spent their fortunes and slaughtered armies in pursuit of that kind of authority. But it can’t be bought or fought for—it’s the charisma of character. His countrymen couldn’t all be Catos, but they could join whichever uncompromising side of the argument Cato was on.