Risking aggression: Toleration of threat & preventive war


Generally speaking, just war theory (JWT) holds that there are two just causes for war: self-defence and ‘other-defence’. The most common type of the latter is popularly known as ‘humanitarian intervention’. There is debate, however, as to whether these can serve as just causes forpreventive war. Those who subscribe to JWT tend to be unified in treating so-called preventive war with a high degree of suspicion on the grounds that it fails to satisfy conventional criteria for jus ad bello; – particularly the just cause and last resort criteria. Francisco di Vitoria held that the only just cause for war was ‘a wrong received’, which renders impossible any justification for preventive war. There are assumptions implicit in recent military practice, however – most notably, the US-led invasion of Iraq in 2003 – that challenge this ban on preventive war.

Interestingly, both supporters and critics attempt to justify their views through the broader logic of JWT; viz., through a conception of what is good for both political communities and individuals, and through a legitimate defence of these goods. Supporters point to situations where so-called rogue states represent ‘grave and imminent risk’ of committing acts of aggression as grounds that justify preventive war; critics argue that to attack another political community on the basis of crimes not yet committed is a breach of the very rights JWT was created to defend.

The advocate of preventive war does not appreciate important aspects concerning the morality of war. In the ongoing tension between Iran and The United States and her allies – if the rhetoric is to be believed – I am asked to tolerate a threat to my security and liberty, and to risk suffering aggression in defence of the rights of the antagonistic, but not yet aggressive, state. The crucial question is how such tolerance and risk fit in with the logic of just war: at what point, if any, does the risk of being attacked become great enough to justify declaring war in anticipation?

In this paper I highlight some of the theoretical and practical difficulties in determining what counts as a grave and imminent threat, focusing especially on the complicated case of ‘imminence’ in the face of so-called ‘Weapons of Mass Destruction’. Secondly, I will argue that not only is the notion of preventive war inconsistent with the defence of the rights of political communities that JWT requires; it is also forbidden by the proportionality requirement of jus ad bellum. A risk of being subjected to aggression is the price for global peace. Whilst political communities can do much to prevent aggression and prepare themselves in case it occurs, the conditions for just war require that this prevention and preparation stop short of declaring war. We must live with a certain degree of risk in this area.


just war theory, preventive war, military ethics, nuclear deterrence, risk, justice

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