The working class is revolutionary or it is nothing.

Constant labor of one uniform kind destroys the intensity and flow of a man's animal spirits, which find recreation and delight in mere change of activity.

Darwin's book is very important and serves me as a basis in natural science for the class struggle in history. One has to put up with the crude English method of development, of course. Despite all deficiencies not only is the death-blow dealt here for the first time to 'teleology' in the natural sciences, but their rational meaning is empirically explained.

Men can see nothing around them that is not their own image; everything speaks to them of themselves. Their very landscape is alive.

All freed, fast-frozen relations, with their train of ancient and venerable prejudices and opinions, are swept away, all new-formed ones become antiquated before they can ossify. 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.

Experience praises the most happy the one who made the most people happy.

Religion is the opium of the masses.