Wrote The Wealth of Nations, in which he argued that wealth was not money in itself, but wealth was derived from the added value in manufactured items produced by both invested capital and labour. Sometimes considered to be the founding father of the laissez-faire economic theory, but in fact argues for some degree of government control in order to maintain equity. Just prior to this he wrote Theory of Moral Sentiments, explaining how it is humans function and interact through what he calls sympathy, setting up important context for The Wealth of Nations.