The Empire of Liberty is a theme developed first by Thomas Jefferson to identify the responsibility of the United States to spread freedom across the world. Jefferson saw the mission of the U.S. in terms of setting an example, expansion into western North America, and by intervention abroad. Major exponents of the theme have been James Monroe (Monroe Doctrine), Andrew Jackson and James K. Polk (manifest destiny), Abraham Lincoln (Gettysburg Address), Theodore Roosevelt (Roosevelt Corollary), Woodrow Wilson (Wilsonianism), Franklin D. Roosevelt, Harry Truman (Truman Doctrine), Ronald Reagan (Reagan Doctrine), Bill Clinton, and George W. Bush.