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.
Nothing can have value without being an object of utility.
The ruling ideas of each age have ever been the ideas of its ruling class.
Revolutions are the locomotives of history.
The production of too many useful things results in too many useless people.
The history of all previous societies has been the history of class struggles.