Jean Charles Léonard de Sismondi, also known as Jean Charles Leonard Simonde de Sismondi,, whose real surname was Simonde, was a Swiss historian and political economist, who is best known for his works on French and Italian history, and his economic ideas. His Nouveaux principes d'économie politique, ou de la richesse dans ses rapports avec la population (1819) represents the first liberal critique of laissez-faire economics. He was one of the pioneering advocates of unemployment insurance, sickness benefits, a progressive tax, regulation of working hours, and a pension scheme. He was also the first to coin the term proletariat to refer to the working class created under capitalism, and his discussion of mieux value anticipates the concept of surplus value. According to Gareth Stedman Jones, "much of what Sismondi wrote became part of the standard repertoire of socialist criticism of modern industry," earning him critical commentary in the Communist Manifesto.

Liberalism is a political and moral philosophy based on the rights of the individual, liberty, consent of the governed, political equality, right to private property and equality before the law. Liberals espouse various and often mutually warring views depending on their understanding of these principles but generally support private property, market economies, individual rights, liberal democracy, secularism, rule of law, economic and political freedom, freedom of speech, freedom of the press, freedom of assembly, and freedom of religion, constitutional government and privacy rights. Liberalism is frequently cited as the dominant ideology of modern history.