The condition of correct intention was a late and distinctly Christian addition to the corpus of just war doctrine. In many ways it was also the most problematic. Although a range of opinion existed among medieval commentators regarding the exact requirements of just cause and proper authority, these two conditions for just war contained criteria that were, at least, relatively easy to identify. The finer details of what constituted self-defence or the proportionate redress of goods might have been subject to different interpretations, but it was often an observable phenomenon if an individual or a territory had been attacked or if goods and property had been damaged or stolen. The same was true concerning the condition of proper authority. Jurists might disagree whether kings as well as emperors had sufficient authority to wage war, but identifying who was a king or an emperor was usually quite straightforward. Of course, even here problems could arise. When a king’s right to rule was seriously challenged, so too was his authority to declare and wage just war: a significant problem when one considers the number of medieval English monarchs who faced challenges to their rule. Imperial authority was also vulnerable to such challenges, particularly when the challenge arose from conflict with the papacy. Henry IV, Frederick II and Ludwig IV are the most notable but certainly not the only German emperors to have faced the challenge of excommunication and ‘deposition’ by the papacy. Despite these potential obstacles, the majority of medieval monarchs, for the majority of the time, enjoyed general recognition of their status and authority. The identification of certain public authorities with sufficient authority to declare war was, then, uncontroversial. Therefore both just cause and proper authority, although possessing qualitative elements, also possessed, to an extent, quantitative elements. They referred to both abstract and material criteria, and it was the material criteria – the property violated or the individual possessing political power – that could be identified and assessed.

The condition of correct intention lacked this quantitative element. The motivation of an individual’s soul was not an observable phenomenon, nor could it be subjected to any quantifiable assessment, especially considering the stark distinction between the peaceful intentions and the violent actions of the just warrior.