An important and rather surprising development in much recent philosophical and public discourse about war has been the endorsement of preventive war. This is clearly related to the Bush administration’s famous (or infamous) enthusiasm for this form of military engagement that they preferred to call preemptive war, a preference which, as many commentators have noted, obscures important moral and political issues.

The widespread discussion of this topic is also bolstered by a concern for two prominent phenomena of the late twentieth and early twenty-first centuries, namely terrorism and extreme political persecution. The first worry gained additional momentum from the attacks in the United States on September 11, 2001 that provoked “the war on terror,” and the second was given additional urgency by the ghastly slaughter in Rwanda during 1994 that helped stimulate a huge debate on the value of armed humanitarian intervention which, having failed to occur in Rwanda, then took place to some extent in Bosnia and fully in Serbia and Kosovo, and was cited by some as justification for the intervention in Iraq. It was also cited in the more recent air power intervention in Libya. In what follows, I want to consider not only the issue of preventive war in the context of state-on-state hostility and political tension, but in the context of contemporary terrorism and, more briefly, humanitarian disaster.