[52] As Madison wrote, "a crisis had arrived which was to decide whether the American experiment was to be a blessing to the world, or to blast for ever the hopes which the republican cause had inspired."[53] He committed to an intense study of law and political theory and also was influenced by Enlightenment texts sent by Jefferson from France.[54] He especially sought out works on international law and the constitutions of "ancient and modern confederacies" such as the Dutch Republic, the Swiss Confederation, and the Achaean League.[55] He came to believe that the United States could improve upon past republican experiments by its size which geographically combined 13 colonies; with so many distinct interests competing against each other, Madison hoped to minimize the abuses of majority rule.[56] Additionally, navigation rights to the major trade routes accessed by the Mississippi River highly concerned Madison. He opposed the proposal by John Jay that the United States concede claims to the river for 25 years, and, according to historian John Ketchum, Madison's desire to fight the proposal was a major motivation in his to return to Congress in 1787.