Theses on Feuerbach, by Karl Marx

Originally published as an appendix to Frederick Engels' "Ludwig Feuerbach and the End of Classical German Philosophy," this brief essay contrasts the purely theoretical materialism of Marx's philosophical predecessors with his practical application of the theory. The final line has become justly famous as a call to arms to materialist philosophers:
"The philosophers have only interpreted the world, in various ways; the point is to change it."