His Riddle of the Modern World (2000) and Making of the Modern World (2001) are contributions to the field of history of ideas, addressing the work of Montesquieu, Adam Smith, Alexis de Tocqueville, Ernest Gellner, Yukichi Fukuzawa and Frederic Maitland.
On 9 February 1860 (18 January in Japanese calendar), the Kanrin Maru, sailed by Katsu Kaishū (as ship captain), John Manjiro, Fukuzawa Yukichi, altogether 96 Japanese sailors, and the American officer John M. Brooke, left Uraga for San Francisco.