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.