icity [to be attained only by peace, justice, and good government, possible only under a single ruler] is in some sort ordained to the end of immortal felicity.
Let Caesar use that reverence toward Peter which a first-born son ought to use toward a father; that, shone upon by the light of paternal grace, he may more powerfully illumine the orb of earth over which he is set by him alone who is the ruler of all things spiritual and temporal.
De Monarchia, § ult. As to the fatal gift of Constantine, Dante demonstrates that an Emperor could not alienate what he held only in trust; but if he made the gift, the Pope should hold it as a feudatory of the Empire, for the benefit, however, of Christ's poor.
De Monarchia, Lib. III. § 10. Poterat tamen Imperator in patrocinium Ecclesiae patrimonium et alia deputare immoto semper superiori dominio cujus unitas divisio non patitur.
Poterat et Vicarius Dei recipere, non tanquam possessor, sed tanquam fructuum pro Ecclesia proque Christi pau