In a publication dedicated to the members of the Liverpool Society for the Mitigation and Gradual Abolition of Slavery, Adam Hodgson writes to the French political economist Jean-Baptiste Say, arguing that slave labour is relatively more expensive than free labour. He bases his argument on an analysis of slave societies which ranges from ancient Rome to the contemporary United States, and cites theorists including Adam Smith, David Hume and the Russian economist Heinrich von Storch.