The success of a democratic society depends, Rawls thought, on members having a shared sense of justice, a common basis for reasoning about what is right. Otherwise, disagreements born from conflicts of interest and identity – and associated “distrust and resentment” – will have corrosive effects on social cooperation. But can we reasonably hope for a broadly shared sense of justice? Religious and philosophical pluralism arguably leave hope for an overlapping consensus on a conception of justice sufficient to cabin those corrosive effects. But what about the pluralism of conceptions of justice themselves? I argue that, even on favorable assumptions about people and social cooperation, we should expect serious disagreement about conceptions of justice and the forms of democracy they recommend, as well as conflicts between and among the interests and identities of citizens who endorse those competing conceptions. Even on these favorable assumptions, then, we have reason to worry – as I think Rawls always did – about the fragility of democracy.

Chapter 2 illustrates how material necessity reflects a two-fold truism that it is in each belligerent’s strategic interest to do what is necessary and to avoid what is unnecessary. The notion evaluates how the means taken advances the ends sought under the prevailing circumstances. A given act can be a military necessity compared to some alternatives, yet a non-necessity compared to some other alternatives. Acts that are wasteful, excessive, inapposite, futile or purposeless are improvable military non-necessities rather than solely the results of war’s irresistible friction. The necessity assessment of particular action cannot be meaningfully generalised or seen outside of its factual context.