This book gives a comprehensive account of the British Idealist approach to international relations from the 1880s to 1930s. In an attempt to historically contextualise the shifts in several British Idealists' approaches to the nature of international relations and human rights, it focuses on their reflections on the Second Boer War, the Great War and the League of Nations. The ensuing discussion offers valuable insights into British Idealists’ evolving approaches to the topics of imperialism, cosmopolitanism, internationalism, multiculturalism and human rights. While the pioneering Idealists like T.H. Green and Bernard Bosanquet are acknowledged as those who set the tone of discussion on these central issues, works by minor British Idealists such as J.S. Mackenzie, J.H. Muirhead, Henry Jones, R.B. Haldane and H.J.W. Hetherington reveal British Idealism’s capacity for adaptation to novel ideational positions under adverse international conditions.