Karl Marx

Hegel remarks somewhere that all facts and personages of great importance in world history occur, as it were, twice. He forgot to add: the first time as a tragedy, the second time as farce.
The Eighteenth Brumaire of Louis Bonaparte
Men make their own history, but they do not make it as they please; they do not make it under self-selected circumstances, but under circumstances existing already, given and transmitted from the past.
The Eighteenth Brumaire of Louis Bonaparte
A specter is haunting Europe—the specter of Communism.
The Manifesto of the Communist Party
The history of all hitherto existing society is the history of class struggles.
The Manifesto of the Communist Party
All that is solid melts into air, all that is holy is profaned, and man is at last compelled to face with sober senses, his real conditions of life, and his relations with his kind.
The Manifesto of the Communist Party
The first premise of all human history is, of course, the existence of living human individuals. Thus the first fact to be established is the physical organisation of these individuals and their consequent relation to the rest of nature.
The German Ideology
in communist society, where nobody has one exclusive sphere of activity but each can become accomplished in any branch he wishes, society regulates the general production and thus makes it possible for me to do one thing today and another tomorrow, to hunt in the morning, to fish in the afternoon, rear cattle in the evening, criticize after dinner, just as I have in mind, without ever becoming hunter, fisherman, shepherd or critic.
The German Ideology
Religious suffering is, at one and the same time, the expression of real suffering and a protest against real suffering. Religion is the sigh of the oppressed creature, the heart of a heartless world, and the soul of soulless conditions. It is the opium of the people.
Critique of Hegel's Philosophy of Right