If in all ideology men and their circumstances appear upside-down as in a camera obscura, this phenomenon arises just as much from their historical life-process as the inversion of objects on the retina does from the physical life-process.
Friedrich EngelsAll history has been a history of class struggles, of struggles between exploited and exploiting, between dominated and dominating classes at various stages of social development.
Friedrich EngelsEverything must justify its existence before the judgment seat of Reason, or give up existence.
Friedrich Engels