200 years after it was written, Adam Smith published The Wealth of Nations, still debated by governments internationally. Smith argued that 'mercantilism'—the theory that the national economy exists solely to strengthen the government, thus the government should regulate the economy—was wrong. Protecting the state from invasion, upholding laws to protect individual freedom, and creating and maintaining public works and institutions that could or would not be undertaken on a smaller scale, he argues, are the sole justifications for government interference in society. And when people are free to pursue their own self-interest within a competitive free market, productivity increases.