  Much better known than De renuntiatione is Giles’ De ecclesiastica potestate, a treatise also composed in defense of Boniface VIII. Most probably in 1302, Giles systematically expounded in this work the views on the relationship between regnum and sacerdotium he had already put forward in a re-discovered sermon held at the papal curia (Luna 1992, Lambertini 2006). The main tenet of his fully fledged argumentation is that the pope, supreme authority of the Church but also of the whole of mankind, is the only legitimate origin of every power on earth, be it exercised — as jurisdiction — on persons, or — as property — on things. In his plenitude of power, the pope possesses an absolute supremacy both in the ecclesiastical and in the temporal sphere, and delegates the exercise of the temporal “sword” to lay sovereigns only in order to fulfill most properly his higher religious duties. Any authority that does not recognize its dependence on the papal power is but usurpation. In Giles’ view, there is no space even for a partially autonomous temporal order. Coherently, Giles maintains that no property rights are valid if they are not legitimated by papal authority.  Interestingly enough, such a claim is also supported by his account of the origin of property, according to which property is not a natural institution, but only the consequence of human agreements, which lack any legitimacy unless they are recognized by the supreme religious power (Miethke 2000, Homann 2004, Krüger 2007). Scholarly discussion about De ecclesiastica potestate is still open. Karl Ubl (2004) argues with strong arguments against previous assumptions, that Giles wrote in reaction to John of Paris’ De regia potestate et papali. While previous scholarship stressed the affinity in form and content between De ecclesiastica potestate and the famous Bull Unam sanctam, Francisco Bertelloni (2004) holds that one should not overlook profound differences between the concepts of papal power that inspire the two texts.