He was a historian whose economic ideas passed through different phases. The acceptance of free trade principles in
De la richesse commerciale was abandoned in favour of a critical posture towards
free trade and industrialisation. ''Nouveaux principes d'économie politique'' attacked wealth accumulation both as an end in itself, and for its detrimental effect on the poor. He indicated contradictions of capitalism. He criticized the harsh conditions endured by the workers from the standpoint of a liberal republican. He warned that industrial competition could create unemployment, overproduction, and unequal distribution of income when economic activity was left without restraint. Later historians of economic thought have described these arguments as an early foundation for welfare economics and broader critiques of capitalism, especially because Sismondi emphasized that economies should serve people rather than treat labor only as a cost of production. He was also a passionate opponent of slavery.
Jean-Baptiste Say referred to Sismondi as "that enlightened author, ingenious, eloquent and selfless". His critique was noticed by
Malthus,
David Ricardo and
J. S. Mill, who called his writing "sprightly, and frequently eloquent". Sismondi's Italian histories were read and esteemed by
Lord Byron,
Percy Bysshe Shelley, and
Stendhal. Sismondi influenced many major socialist thinkers including
Karl Marx,
Rosa Luxemburg, and
Robert Owen. Marx thought Sismondi embodied the critique of the "bourgeois science of economics". In his notes, Marx excerpted various aspects of his analysis. Marx was particularly fond of Sismondi's statement that "The Roman proletariat lived almost exclusively at the expense of society. One could almost say that modern society lives at the expense of the proletariat, from the share which it deducts from the reward of his labor." In 1897,
Vladimir Lenin wrote an article refuting Sismondi's work. Lenin said, The contributor to
Russkoye Bogatstvo states at the very outset that no writer has been "so wrongly appraised" as Sismondi, who, he alleges, has been "unjustly" represented, now as a reactionary, then as a utopian. The very opposite is true. Precisely this appraisal of Sismondi is quite correct. In 1913, Rosa Luxemburg wrote a critique of Sismondi in
The Accumulation of Capital. The historian
Jerzy Jedlicki writes: All sorts of labels were pinned on this humanist from Geneva who lived in the period of the beginnings of industrial capitalism: he was regarded as a reactionary and a radical, a petty-bourgeois socialist and a romanticist. But when we read his work a hundred and fifty years later, we discover in him a precursor of the democratized, corrective liberalism of the twentieth century and also, in spite of all the defects of his economic theory, a precursor of concepts for the development of overpopulated countries with a low national income. Sismondi’s thought, unfettered by doctrine, has stood the test of time, something which cannot be said of many of his contemporaries. == Main publications ==