Jean Charles Leonard de Sismondi, a Swiss economist and historian, warns against the socioeconomic effects of unregulated industrialism in his New Principles of Political Economy.
As an economist, Sismondi represents a humanitarian protest against the dominant orthodoxy of his time.
In his 1803 book, he had followed Adam Smith; but in his principal subsequent economic work, Nouveaux principes d'économie politique (1819), he insists on the fact that economic science studies the means of increasing wealth too much, and the use of wealth for producing happiness, too little.
For the science of economics, his most important contribution is probably his discovery of economic cycles.
His theory may more precisely be classed as one of periodic crises, rather than cycles per se, and as such is the earliest theorist of systemic Crisis theory.
His theory will be adapted by Charles Dunoyer, who will introduce the notion of cycling between two phases, thus giving a modern form of economic cycle.
