As an economist, Sismondi represented a humanitarian protest against the dominant orthodoxy of his time. In his 1803 book, he followed Adam Smith; but in his principal subsequent economic work, "Nouveaux principes d'économie politique" (1819), he insisted on the fact that economic science studied 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 was probably his discovery of economic cycles. In refutation of other thinkers at the time (notably J. B. Say and David Ricardo), Sismondi challenged the idea that economic equilibrium leading to full employment would be immediately and spontaneously achieved. He wrote, "Let us beware of this dangerous theory of equilibrium which is supposed to be automatically established. A certain kind of equilibrium, it is true, is reestablished in the long run, but it is after a frightful amount of suffering." While he was not a socialist, in protesting against laissez faire and invoking the state "to regulate the progress of wealth" he was an interesting precursor of the German Historical school of economics.