Classical political economy highlights notions which are very useful today in development debates. Foreign trade is the source of wealth for the Mercantilists. Land and labour occupy centre stage with Petty and Quesnay, agricultural surplus is the core of reproduction and economic growth. Human rights and Montesquieu’s separation of powers emerge during the Enlightenment. Smith emphasizes a new source of wealth: the division of labour and higher labour productivity, which depend on the accumulation of capital. Smith and Ricardo attack Mercantilist doctrines, but their support of free trade is much more articulated than what appears in the mainstream interpretation. Marx analyses the crises in a capitalist economy. The classical economists highlight the difference between use values and exchange values in the process of economic and social reproduction.