Adam Smith was a famous economist and moral philosopher, who pioneered the economic principle of free enterprise. His best known work, `The Wealth of Nations? of 1776, describes how the individual pursuit of self-interest leads to greater prosperity and the common good of society. Smith was a complex intellectual figure and shared the ethical concerns of his great friend, David Hume. Another friend, Dugald Stewart, once remarked that "his features were brightened by a smile of inexpressible benignity". That smile is clearly visible in this portrait by an unknown artist, which is known as the `Muir portrait? after the family who once owned it. The portrait was probably painted posthumously, based on a medallion by James Tassie.