“Let the ruling classes tremble at a communist revolution. The proletarians have nothing to lose but their chains. They have a world to win. Workingmen of all countries, unite!”

“Workers of the world unite; you have nothing to lose but your chains.”

“Reason has always existed, but not always in a reasonable form.”

“There is no royal road to science, and only those who do not dread the fatiguing climb of its steep paths have a chance of gaining its luminous summits.”