Adam Smith (1723–1790), a Scottish political economist and philosopher, is considered one of the most influential economists of all time for his work The Wealth of Nations (1776). Smith is best known for his explanation of how rational self-interest in a free-market economy can lead to improved economic well-being for all. The main cause of prosperity, argued Smith, was increasing division of labor that boosted labor productivity and hence wages. Smith was opposed to monopolies and the concepts of mercantilism—the practice of artificially maintaining a trade surplus—but admitted restrictions to free trade were sometimes necessary as national economic weapons. The primary advantage of trade, he argued, was that it opened up new markets for surplus goods and also provided some commodities at less cost from abroad than at home. Smith’s views on free markets and free trade are dominant themes in economic and political life today, which explains why The Wealth of Nations remains the most important book ever written on the subject of political economy