Because the poorest people tend to die from easily preventable diseases, addressing poverty is a relatively cheap way to save lives. War, by contrast, is extremely expensive. This article argues that, since states that wage war could alleviate poverty instead, poverty can render war unjust. Two just war theory conditions prove relevant: proportionality and last resort. Proportionality requires that war does not yield excessive costs in relation to the benefits. Standardly, just war theorists count only the direct costs: the death (...) and destruction wrought by war. This article argues that it can sometimes be appropriate to add the opportunity costs of a failure to alleviate poverty. Last resort is the condition that there must be no better alternative means of achieving the same just end for which the war is waged. This article argues that there are some cases in which alleviating poverty may constitute a better alternative. These are cases in which the most fitting description of the just end for war is sufficiently general that poverty alleviation offers a means to pursue it. The idea that poverty can sometimes render war unjust has, to date, been largely overlooked. It is, nevertheless, an idea with profound implications since, once taken seriously, war becomes much harder to justify. Wars that, in every other respect, seem just may prove disproportionate or unnecessary given the alternative of alleviating poverty. (shrink)

An “optional war” is a war that a state is permitted but not required to wage. Are there any such wars? This article assesses the two most promising arguments for optional war. (1) Permissible humanitarian wars can be so costly for soldiers and taxpayers that states are not be required them. (2) Wars of national self-defense can be discretionary: states can sometimes choose whether or not to defend themselves. The article refutes both arguments. Pace (1), states should not wage wars (...) when the costs of doing so are overly burdensome. Pace (2), states are required to resist aggression whenever they are morally permitted to do so. (shrink)

Discounting future costs and benefits is often defended on the ground that our descendants will be richer. Simply to treat the future as better off, however, is to commit an ecological fallacy. Even if our descendants are better off when we average across climate change scenarios, this cannot justify discounting costs and benefits in possible states of the world in which they are not. Giving due weight to catastrophe scenarios requires energetic action against climate change.