This son of Mary, Queen of Scots was the sixth of his name in Scotland, and he was succeeded by his son Charles I.  
This "wisest fool in Christendom" argued for the divine right of kings as an extension of apostolic succession in The True Law of Free Monarchy.  His attempt to marry his son to the Infanta Maria of Spain led to a major religious controversy, and he was the target of the plan by Robert Catesby and Guy Fawkes to blow up Parliament, the Gunpowder Plot.  This son of Mary, Queen of Scots was the sixth of his name in Scotland, and he was succeeded by his son Charles I.  For 10 points, name this English king who succeeded Elizabeth I in 1603 and founded the House of Stuart.
This "wisest fool in Christendom" argued for the divine right of kings as an extension of apostolic succession in The True Law of Free Monarchy.  
{James I} [accept {James VI} of {Scotland} before "{sixth}"]