The only legitimate society is the City of God, the earthly portion of which is the Catholic Church (militant). The visible head (and supreme earthly judge) of the members of the Church is the Pope. The ecclesiastical hierarchy which governs the Church militant is forbidden to administer earthly affairs (that is: matters pertaining to property, autonomy and marriage) beyond the bare necessities required to sustain the preaching of the Gospel, the administration of the sacraments and the maintenance of the canons. Those lay Christians who have not been given the graces necessary to bind themselves to the counsels by vow are obliged to continue to administer earthly affairs and require a social authority to do so. This authority is called the temporal power as distinct from the spiritual power exercised by the ecclesiastical hierarchy. As temporal goods are ordered to the supernatural final end those who exercise the temporal power do so subject to the judgement of the spiritual power and may do so legitimately only if they are members of the Church militant (a question subject to the judgment of the spiritual power). Inside the Church an apostate prince loses power ipso facto.
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A temporal community is inside the Church when by its constitutional law it fulfils its obligation to submit to the ecclesiastical hierarchy. This is an obligation consequent upon the obligation of natural law upon all men and communities of men to recognise and embrace the true religion. Once this obligation is fulfilled the temporal community necessarily recognises its limited jurisdiction over earthly affairs and submits to the supreme jurisdiction of the ecclesiastical hierarchy.
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The temporal power is a necessary part of human life and consequently whosoever exercises it outside the Church the faithful must submit to that authority whenever it does not conflict with natural or divine law (even though such a person ex hypothesi fails in his obligation to worship God individually and qua ruler in the manner God has appointed). Inside the Church a temporal authority which is judged to have sinfully misused the temporal power may be sanctioned and if necessary deposed by the ecclesiastical hierarchy. Outside the Church this power would equally obtain were it not that it would contravene the divine law prohibition on forcible conversion. Those in the Church who exercise the temporal sword may do so upon their own initiative or as directed by the spiritual power to chastise or depose those outside the Church who grossly and obstinately violate the natural law or prevent the preaching of the Gospel, or (inside the Church) to execute the sentence of the spiritual power against an offending member of the faithful (including a delinquent wielder of the temporal power).
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In the appointment of the temporal ruler in the Church the relevant civil laws are to be followed. In the event that these laws are entirely frustrated (whether on account of their own failure in particulars or because they cannot be obeyed without sin) the spiritual power may exceptionally appoint the temporal ruler. This is exceptional because the appointment of the wielder of the temporal sword is itself an exercise of the temporal sword which the holder of the spiritual sword may not ordinarily wield. The civil laws may allot to the spiritual power the authority regularly to appoint (or participate in the appointment of) the temporal ruler only where this is unavoidable to sustain the preaching of the Gospel, the administration of the sacraments and the maintenance of the canons. This will generally be the case in regard to the election of the emperor and the appointment of the administrators of the papal state but in other instances only in exceptional (though potentially prolonged e.g. the Dark Ages) circumstances. The temporal power may coerce in regard to divine law only as directed by the spiritual power and only inside the Church. It may proscribe idolatry and the promotion of irreligion even prior to fulfilling its obligation to recognise and embrace the true religion.
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