The product of mental labor - science - always stands far below its value, because the labor-time necessary to reproduce it has no relation at all to the labor-time required for its original production.
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.