The classic, theological tradition of just war reasoning (JWT) is not exhausted but needed more than ever in the shadow of global risks, when facing “hybrid” war, and when the difference between war and peace is said to be blurring. The tradition does not speak with one voice but debate within the tradition about the (un)acceptability of military action under conditions of uncertainty sheds light, in at least three ways, on ways of approaching the range of unorthodox tactics threated in conflict today:

1. 1. How to be fearful. Fear and anxiety in an age of risk are potential threats to reason. The JWT has resources with which to consider “how to fear” wisely.

2. 2. How to grapple with issues of classification, including what constitutes an attack equivalent to an “armed attack” under UN Charter Art 51. When, for instance, are cyber-attacks better dealt with under civilian, international commercial law, and when the laws of war?

3. 3. How to approach new challenges in a principled manner. Are different principles or criteria needed to govern action (e.g., the criterion of intensity) or do immediacy and necessity remain the most critically important principles in our moral arsenal?