"Wherever big industries displaced manufacture, the bourgeoisie developed in wealth and power to the utmost and made itself the first class of the country. ... Everywhere the proletariat develops in step with the bourgeoisie. In proportion, as the bourgeoisie grows in wealth, the proletariat grows in numbers. For, since the proletarians can be employed only by capital, and since capital extends only through employing labor, it follows that the growth of the proletariat proceeds at precisely the same pace as the growth of capital."