Natural science will in time incorporate into itself the science of man, just as the science of man will incorporate into itself natural science: there will be one science.

Force is the midwife of every old society pregnant with a new one.

Is it a misfortune that magnificent California was seized from the lazy Mexicans who did not know what to do with it.

Under private property, each tries to establish over the other an alien power, so as thereby to find satisfaction of his own selfish need. The increase in the quantity of objects is therefore accompanied by an extension of the realm of the alien powers to which man is subjected, and every new product represents a new potentiality of mutual swindling and mutual plundering.

In the various stages of development which the struggle of working class against the bourgeoisie has to pass through, they always and everywhere represent the interests of the movement as a whole.

Modern bourgeois society with its relations of production, of exchange, and of property, a society that has conjured up such gigantic means of production and of exchange, is like the sorcerer, who is no longer able to control the powers of the nether world whom he has called up by his spells.

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. (Preface to the French edition).