Throughout history, some books have changed the world. They have transformed the way we see ourselves - and each other. They have inspired debate, dissent, war and revolution. They have enlightened, outraged, provoked and comforted. They have enriched lives - and destroyed them. Now Penguin brings you the works of the great thinkers, pioneers, radicals and visionaries whose ideas shook civilization, and helped make us who we are.

'Do not act as if you had ten thousand years to live ... while you have life in you, while you still can, make yourself good.' The Meditations of Marcus Aurelius (AD 121-180) is a private notebook of philosophical reflections, written by a Roman emperor probably on military campaign in Germany.

In short, highly charged comments, Marcus draws on Stoic philosophy to confront challenges that he felt acutely, but which are also shared by all human beings - the looming presence of death, making sense of one's social role and projects, the moral significance of the universe. They bring us closer to the personality of the emperor, who is often disillusioned with his own status and with human activities in general; they are both an historical document and a remarkable spiritual diary.