Popular sovereignty was seen on the issue of slavery as a political middle ground. Popular sovereignty is the principle that people should rule, and as such the status of slavery should be determined by the votes of local settlers and not congress.
During the Mexican War, when slavery became a political problem, Douglas faced a challenge. Fearing that the issue would interfere with the Constitution, he argued for the doctrine of popular sovereignty — the right of the people of a state or territory to determine for themselves the question of slavery — as a solution for the sake of the Union. He led the congressional struggle for the 18th compromise.
Nations that gained or regained territory or independence after World War I. France: gained Alsace-Lorraine as well as various African colonies from the German Empire, and Middle East territories from the Ottoman Empire. The African and Middle East gains were officially League of Nations Mandates.
His political philosophies form its foundation John Locke was a very famous Enlightenment philosopher featuring a plethora of individualism in both his concepts and beliefs. Hope this helps! :)