In countries where modern civilization has become fully developed, a new class of petty bourgeois has been formed, fluctuating between proletariat and bourgeoisie, and ever renewing itself as a supplementary part of bourgeois society. The individual members of this class, however, are being constantly hurled down into the proletariat by the action of competition and as modern industry develops, they even see the moment approaching when they will completely disappear as an independent section of modern society to be replaced in manufactures, agriculture and commerce, by overlookers, bailiffs and shopmen.

In countries like France, where the peasants constitute far more than half of the population, it was natural that writers who sided with the proletariat against the bourgeoisie, should use in their criticism of the bourgeois regime, the standard of the peasant and petty bourgeois, and from the standpoint of these intermediate classes should take up the cudgels for the working class. Thus arose petty bourgeois Socialism. Sismondi was the head of this school, not only in France but also in England.