Leviathan is a seventeenth-century work on what the author felt was a good structure for society and legitimate government. The book was written during the English Civil War, and argues for a social contract between an absolute sovereign and the subjects of a commonwealth. While the work was written with the social structures of the time as influences, it also addresses many questions regarding the elements of the civil society that are still debated today. These include concepts of ex post facto law, fair tax structure, and the difference between natural law and civil law, among others. This book rightly ranks among the top treatises on government and statecraft in Western Civilization.