This book could be seen as a reply to Nigel Biggar's huge book In Defence of War (OUP, 2013). For it is a systematic and well-informed account of ways of resolving conflicts without violence. And if what it says is true, then it is extremely important. But how far is it true?

Sider begins with brief accounts of non-violent actions in the ancient world, as related for example in Exodus (Chapters 1 and 2) and by Josephus. He also discusses Leo the Great's negotiations with Attila the Hun. The book then goes on to remind us of non-violent actions in the 1920s and 1930s before we encounter two longer chapters on Gandhi (‘Defeating the British Empire’) and Martin Luther King (‘The Battle Against American Racism’). Part 1 of the book concludes with accounts of the successful non-violent campaigns of opposition to Somoza's dictatorship in Nicaragua (with the ‘Witness for Peace’ organisation) and to the tyranny of the Marcos regime in the Philippines. Part 2 is devoted to the non-violent successes of the Solidarity campaign against the Soviet empire in Poland and to the overthrow of the Communist dictatorship in East Germany. Part 3 discusses three more recent examples: the successful non-violent campaign by the women of Liberia against the tyranny of Charles Taylor; the toppling of the dictators in Tunisia and Egypt in the ‘Arab Spring’; and the growth of small non-violent teams of volunteers ready to work wherever they are needed, such as the Peace Brigades International, Christian Peacemaker Teams (mostly notably the Mennonites), Muslim Peacemaker Teams, the Ecumenical Accompaniment Programme in Palestine and Israel, and the Nonviolent Peaceforce (an American-inspired body founded at a conference in India). Finally, in part 4 the author reflects on the experiences he has outlined, calling for ‘a vast exploration of non-violent alternatives’ and arguing (echoing William James) that non-violence is ‘the moral equivalent of war’. He adds a valuable bibliography of works devoted to the study of non-violent action.

A difference between this book and Nigel Biggar's is that the latter takes as its starting point that war means armed conflict between sovereign states. While he is very clear that the concept of a ‘just war’ predates the arrival of the modern sovereign state, which (as Philip Bobbit shows, in his massive The Shield of Achilles) emerged only with the collapse of the European mediaeval system in the sixteenth and seventeenth centuries, Biggar nevertheless concentrates on the twentieth and twenty-first centuries. And his final chapter argues that even the war initiated in 2003 against Iraq was a ‘just war’, contrary to what many other just war analysts (such as David Fisher, in his The Morality of War) have maintained. But Biggar does not consider campaigns taking place within states, such as insurrections and the like. Whereas much of Sider's argument is designed to show that such campaigns of non-violent action can be both just and successful in achieving their goals. Nevertheless the question remains: can non-violence ever be successful (and if not then it cannot be just either) when conducting conflicts between the governments and peoples of modern sovereign states? Could non-violence ever have defeated (say) Hitler? Biggar's book implies that it could not.

Despite Sider's careful analyses of the strengths and weaknesses of non-violent campaigns, his emphasis is on the ethical advantages of non-violent over violent strategies. But he does not ask himself how non-violently to combat the small but well paid, equipped and trained armies of modern states or their sophisticated weaponry. And even more telling is the question of how to recruit, train and keep ready the huge numbers of non-violent volunteers (not likely to be well-paid or equipped) that Sider sees are required to confront or replace professional soldiers employed by governments. For professional soldiers are recruited partly to compensate for the lack of military prowess or inclination prevailing among most of any state's civilian population. True, the campaigns of Gandhi and Martin Luther King recruited huge numbers of non-violent supporters, from those who were energised by the campaigns themselves, and these supporters were key to their successes. But they did not maintain these volunteer non-violent armies once the campaign was over. Sider's case for a standing army of willing, but mostly unpaid volunteers ready and able to deal with likely possible crises whenever and wherever these arise, is not convincing, however desirable it may be. Governments of states maintain standing armies of professionals precisely because most of their populations are otherwise occupied in the state economy. Given this fact, recruiting an ‘army’ of non-violent volunteers to match these professionals is surely an impossible dream. Most Christians have never really tried it, not just because they have not been inspired to do so, but because they have other equally Christian ways of spending their time.

But if Sider cannot convince us of the practicability of his non-violent strategy against the armies of modern state-governments, Biggar fails to address the hugely important question of how to deal with terrorism or of the break-up of the state itself. Just war theory insists on the need for state authority for going to war, but does not, indeed cannot, query the very existence of the state itself, as in the case of Ukraine. Neither does it address the justice or otherwise of the violence of IS or Boko Haram or other modern terrorist movements, let alone how to meet it. Whether Sider's case for non-violence can address these fundamental questions any better than Biggar is a matter for serious debate. To me the answer is not clear. What is clear, however, is that humanity's Hobbesian existence within a pattern of competing sovereign states on the surface of our planet, without any over-arching authority, is under threat from climate change, the internet, the prevalence of global markets for goods and services, etc. etc. I doubt whether either non-violence or just war can cope with these huge new dangers. Perhaps the European Union is pointing the right way.