In 1915 he was succeeded in the office of President of the "Académie des Sciences morales et politiques" by Alexandre Ribot, and then delivered a discourse on "The Evolution of German Imperialism". Meanwhile, he found time to issue at the request of the Minister of Public Instruction a brief summary of French Philosophy. Bergson did a large amount of traveling and lecturing in America during the war. He participated in the negotiations which led to the entry of the United States in the war. He was there when the French Mission under René Viviani paid a visit in April and May 1917, following upon America's entry into the conflict. Viviani's book "La Mission française en Amérique" (1917), contains a preface by Bergson.