Marcus Aurelius, called the Philosopher, was Roman emperor from 161 to 180. He ruled the Roman Empire with his adoptive brother, Lucius Verus, until Lucius' death in 169. He was the last of the rulers traditionally known as the Five Good Emperors. He is also seen as the last emperor of the Pax Romana, an age of relative peace and stability for the Empire. Marcus' personal philosophical writings, often called Meditations, are a significant source of the modern understanding of ancient Stoic philosophy. They have been praised by fellow writers, philosophers, and monarchs–as well as by poets and politicians–centuries after his death.