Life is not determined by consciousness, but consciousness by life.

Political economy regards the proletarian like a horse, he must receive enough to enable him to work. It does not consider him, during the time when he is not working, as a human being. It leaves this to criminal law, doctors, religion, statistical tables, politics, and the beadle.

Science and democracy are the right and left hands of what I'll refer to as the move from the realm of necessity to the realm of freedom.

Philosophy is to science as masturbation is to sex.

Capital brings forth living offspring, or at the least, lays the golden eggs.

Once the inner connection is grasped, all theoretical belief in the permanent necessity of existing conditions collapses before their collapse in practice -- Letter to Ludwig Kugelmann (July 11, 1868)

The more of himself man attributes to God, the less he has left in himself.