The Wealth of Nations
Smith said markets should be free. At the time, some big companies (like the East India Company) were controlled by the government. Sometimes the rulers made laws that were good for themselves but not for workers or customers. For example, in the American colonies, colonists could grow cotton but were not allowed to make clothing from it. They had to ship it to England to be made into clothing, then buy it back after it was finished. Smith said this was bad for individuals and for society. He thought it was better for money to flow freely and naturally between buyers and sellers without outside interference. Money would naturally go to the sellers who made the best product at the best price. This way if people did what was best for them, it would end up being best for society as a whole, almost like an "invisible hand" was guiding everything.