 Locke took a more favorable stance toward revolution than Hobbes or his medieval predecessors, because he did not believe that the risks of physical insecurity attendant upon the destruction of an existing government were as high as those thinkers did. That more optimistic view as grounded, in turn, in his belief that the destruction of the political order need not entail the destruction of society—that is, of social practices and habits that effectively control the most serious forms of violence. It is a mistake, however, to conclude either that Hobbes was right and Locke was wrong or vice versa about the consequences for physical security of the destruction of government. A generalization either way would be unhelpful. A more reasonable view is that the risks of the destruction of government and hence of revolution vary, depending upon the circumstances. If that is so, and if the justifiability of revolution depends even in part on the severity of the risks of physical insecurity it involves, then it appears that the content of a theory of just revolutionary war must be shaped by empirical considerations. Yet it is fair to say that many philosophers who have had something to say about just revolutionary war, whether explicitly or by implication in their work on interstate wars, have not taken this point to heart. They have either not understood the importance of empirical assumptions about the risks of revolution or made the relevant empirical assumptions but without supplying sufficient evidence for their validity. Without a well-evidenced empirical account of the conditions under which attempts to overthrow the government are likely to cause violent anarchy, and an account of the conditions under which violent anarchy is likely to continue for some significant period of time, both pessimism and optimism about revolution, and the calculations of proportionality on which the justification for revolution is supposed to depend, will be more a matter of faith than reason.