St. Robert Bellarmine
That the Pope possesses the highest temporal power indirectly.
The opinion of theologians must first be explained and then proven. As to the first, we affirm that the Pontiff as Pontiff, even though he does not have any merely temporal power, nevertheless has the greatest spiritual power of making disposition of temporal matters that are directed to a spiritual good: many explain this by similes that refer to a "fraenifactoriam" skill ["rein-making skill"], to an equestrian skill, and the like. Inasmuch as those two skills are different from each other, because they have different objects, subjects, and actions, nevertheless, because the purpose of the one is ordered to the purpose of the other, therefore one takes precedence over the other and prescribes the rules for it; so the ecclesiastical and the political powers appear distinct from each other and, nevertheless, one is subordinate to the other, because the purpose of the one by its nature has a reference to the other.
But this similitude is not altogether suitable, for in those skills the inferior exists only on account of the superior, in such a way that, if the higher is removed, the inferior disappears directly: for if there were no equestrian art, certainly a rein-making skill would be superfluous. But the political power does not exist only because of the ecclesiastical, for even if there were no ecclesiastical power, there would still be a political, as is manifest in infidel lands, where there is true temporal and political power, nevertheless, without any relationship to a true ecclesiastical and spiritual power.
There is, however, an available simile far more apt, by which Gregory Nazianzen explains this very matter. And following him, Hugo of St. Victor, Thomas Waldensis, John Driedo and Victor de Soto. For as spirit and flesh are present in man, so there are in the Church those two powers: for the flesh and the spirit are like two republics which can be found both separate and conjoined. The flesh has sensory powers and appetites to which correspond proportionate acts and powers, and of all of them the built-in purpose is health and the good constitution of the body. The spirit [spiritual soul] has intellect and will and their proportionate acts and objects, and for their purpose the health and perfection of the soul: flesh can be found without the spirit in animals while the spirit can be found without flesh in the angels.
From this example, it appears that neither component exists precisely just for the other. For flesh is found conjoined with spirit in man, when, because they constitute one person, they necessarily have union and subordination: for the flesh is subordinate and the spirit is primary, and although the spirit does not mingle with the acts of the flesh but allows the flesh to perform its own actions, as the flesh does in animals, nevertheless, when those actions affect the purpose of the spirit itself, the spirit commands the flesh and even castigates it, and, if necessary, imposes fasts and other afflictions, even with some detriment to and weakening of the body, and forces the tongue not to speak and the eyes to refrain from looking, etc. For a similar reason, if some activity of the body is necessary to obtain an objective of the spirit, even death itself, the spirit can command the body to expose itself and its powers, as we see Martyrs doing.
Entirely in the same way, the political power has its own princes, laws, justices, and the like, and likewise, the ecclesiastical power has its Bishops, canons, and tribunals. The former has for its purpose temporal peace and the latter, eternal salvation. Sometimes they are found separated, as formerly, in the time of the Apostles, sometimes the two powers are bound together, as now: when they are found joined together, they constitute one body, and, therefore, they need to be connected, and the inferior power subject and subordinate to the higher. Therefore, the spiritual power does not mix in temporal business but leaves everything proceed in the way it did before the two powers were joined together, provided that the temporal affairs do not present an obstacle to the spiritual purpose or are not necessary for attaining that purpose. If, however, something of that sort happens, the spiritual power can and ought to coerce the temporal power by every reason and way that seem necessary.
In order, however, that we might explain all these considerations in their particulars, the spiritual power of the Pope must be compared with the persons of judges and secular rulers, with their civil laws, and with their courts and decisions.
As far as persons are concerned, the Pope cannot ordinarily depose temporal rulers, even for just causes, in the same way he deposes bishops, that is, as their usual Judge: nevertheless, he can change kingdoms and take from one and give to another, if it be necessary for the salvation of souls, as we will prove. As far as laws are concerned, the Pope as Pope cannot ordinarily establish a civil law or confirm or modify laws of rulers because he is not a political ruler of the Church: nevertheless, he can do all that, if some civil law is necessary for the salvation of souls while kings are unwilling to establish it; or if there are other harms to souls and kings are unwilling to abolish them.
Therefore, that rule is excellent which the Gloss ("ad cap. Possessor, de reg. Jur. in Sexto, quae talis est"). When Imperial and Pontifical laws are found to be contradictory on the same matter, if the content of the law is a regulation containing danger to souls, the Imperial law is abrogated by the Pontiff....But when the matter of the law is a temporal affair unrelated to a danger to souls, the law of a Pontiff cannot abrogate an imperial law, but both laws must be observed, the one in the ecclesiastical jurisdiction, the other in the civil forum.
As far as judicial decisions are concerned, the Pope as Pope cannot ordinarily give judicial decisions relating to temporal matters: for Bernard rightly says to Eugenius (in the first book "De Consideratione"): "These terrestrial and lower concerns have their own Judges, the Kings and Rulers of the earth. To what purpose should you invade the preserve of others?" Likewise: "Your power is over crimes not possessions." But, nevertheless, in a case where it is necessary for the salvation of souls, the Pontiff can also pass temporal judgments, when, namely, there is no one who could pass judgment, as when two sovereign Kings are at odds, or when those who can and ought to pass judgment, do not want to make a decision. And Innocent the Third says that the Pontiff exercises temporal jurisdiction only occasionally.