This opinion can be proved both by reasons and by examples.
A first reason for holding it is: The civil power is subject to the spiritual power when both are parts of a Christian Republic; therefore, the spiritual head can command temporal rulers and make dispositions of temporal matters in ordering them to a spiritual good: for every superior can command his inferior.
That, however, the political power, not only when Christian, but simply as political, is as such subject to the ecclesiastical power. First, it can be demonstrated from the purposes of both. For a temporal purpose is subordinate to a spiritual, as is manifest; because temporal happiness is not the absolutely ultimate end [of man]; as temporary it must be related to what is unending: this is made clear by Aristotle in Bk I of his Ethics, c. 1, that faculties or powers are subordinated as are purposes.
Secondly, Kings and Pontiffs, clerics and laity, do not form two republics but one, that is, one Church: For we are all one body (Rom. XII and I Cor., XII); but in all bodies, the members are connected and dependent one upon another: but it is not right to assert that spiritual matters are dependent on temporal affairs; therefore, temporal matters depend upon the spiritual and are subject to them.
Thirdly, if a temporal administration impedes a spiritual good, in the opinion of all, the temporal ruler is bound to change that mode of administration, even to the detriment of a temporal good; therefore, this is a sign that the temporal power depends on the spiritual and that the temporal power is subject to the spiritual.
Nor would it be sufficient to reply: that the Ruler is obliged to change an aspect of his administration, not, however, because of a subjection or a subordination to a spiritual power, but only because of the order of charity by which we are obliged to place greater goods ahead of lesser goods; for, not for the sake of the order of charity is one republic held to suffer harm lest another, more noble republic suffer harm. And a private person who is obliged to give all his goods for the preservation of his republic is nevertheless not held to do the same for another, however more worthy. If, then, a temporal republic is obliged to suffer a setback because of a spiritual good, it is a sign that the two are not separate but two parts of one and the same thing, and that one is subordinate to the other.
Nor is it valid to say: A temporal ruler is obliged to suffer a temporal loss for the sake of a spiritual good, not because of subjection to a spiritual republic, but because, otherwise, he would do harm to his subjects, for whom it is evil to lose spiritual goods for the sake of temporal goods. For men of another kingdom, even if they were not its subjects, may suffer notable damage in spiritual concerns on account of the temporal administration of any Christian king; in such an event, such a ruler is obliged to change his way of administering; no other reason can be given for this except that they are members of the same body and subject one to the other.
A second reason. An ecclesiastical republic ought to be a complete one [“perfecta”] and sufficient unto itself to its purpose: of such a kind are well-founded republics; therefore it [an ecclesiastical republic] should have all power necessary to attain its end: but necessary is the power to use and dispose of temporal things, because otherwise, evil rulers could foment heresies and subvert religion; therefore, it has such power.
Similarly, any republic can, because it is a complete thing and self-sufficient, can command another republic not subject to it to change its administration, and even to depose its ruler and install another, when it cannot otherwise defend itself from injustices; there, even more rightly could a spiritual republic command a temporal republic subject to it, and force it to change its manner of administration and depose rulers and substitute others, when, otherwise, it cannot safeguard its spiritual good; and in this way are to be understood the words of St. Bernard in the fourth book of “De Consideratione,” and Boniface VIII, in Extrav. Unam Sanctam, where they say that within the power of the Pope are both “swords.” For they wish to signify that the Pontiff has per se, both his own spiritual sword and, because the temporal sword is subject to the spiritual, the Pontiff can command the king, or prohibit the use of the temporal sword, when the necessity of the Church requires it.
In this vein are the words of St. Bernard, which Boniface has imitated: “Why do you (he says, addressing the Pope) attempt to usurp the sword which you once ordered to be placed back in the scabbard? That you have denied it is yours does not seem to have paid sufficient attention to the words of the Lord when He says, ‘Return your sword to its sheath.’ Yours, therefore, it is, and, if not perhaps by your wish and if it is not to be unsheathed by your hand, or otherwise does not belong to you, why should the Lord have responded to the Apostles when they said, ‘Look, here are two swords,’ by saying, ‘That is sufficient,’ rather than, ‘That is too much.’ Both therefore belong to the Church, namely, the spiritual sword and the material, and the one is to be wielded for the Church and the other by the Church. One by the hand of a priest, the other by the hand of a soldier but by the approval of the priest and at the signal of the Emperor.” Where it should be noted that when the heretics reprehend Boniface as erroneous, arrogant, tyrranical (thus they speak about him here and there), they should be warned the words of Bernard are the same (in his book “De Consider.”, where, nevertheless, he speaks without adulation) as those of Calvin (in “lib. IV Inst. c. 11, paragraph 10); so Bernard speaks, in order that truth itself may seem to speak.
A third reason. It is not permitted to Christians to tolerate an infidel king, or a heretical one, if he strives to draw his subjects to embrace heresy or infidelity; but to judge whether a King is drawing to heresy or not, belongs to the competence of the Pontiff, to whom the care of religion is committed. Therefore, it belongs to the Pontiff to judge whether a king should be deposed or not be deposed.
The proposition above is proved from chapter XVII of Deuteronomy, where the people are forbidden to choose a king who is not one of the brothers, that is a Jew, but one of other brothers not Jewish, lest he draw Jews to idolatry; therefore, Christians, also, are forbidden to choose a king who is non-Christian: for the precept is a moral one and rests on natural imperatives. Again, it is of the same order of danger and harm to choose a non-Christian as not to depose a non-Christian in power if he attempts to turn the people away from their Faith. I add, however, that last condition, on account of those infidel rulers who had dominion over their people before they were converted to the Faith: for if such rulers were not to attempt to turn the faithful away from their faith, they could indeed be deprived of authority, in the opinion of St. Thomas (in 2.2. q. X, ar. 10), but the Church does not always so deprive them, either because it lacks the strength or because it does not judge it expedient. But if the same rulers should attempt to turn the people away from the Faith, in the opinion of all, it can and should deprive them of their authority.
But if Christians formerly did not depose Nero, Diocletian, Julian the Apostate, Valens the Arian, and the like, it was because temporal power was lacking to Christians. For, that they otherwise could have done it rightfully, is clear from the Apostle, in I Corinthians, VI, where he commands that new judges of their temporal cases be instituted by Christians, in order that Christians be not forced to present their cases before a judge who is a persecutor of Christ; as in this way new judges could be installed; so, too, both new princes and kings could have been established, if power to do so had been had.
Furthermore, to tolerate a heretical or infidel king who is trying to draw people to his sect is to expose religion to a most evident danger: “For such as is the ruler of a city, of the same kind are its inhabitants.” (Eccl. X, 2), whence the saying, “The world is made after the example of the king.” And experience teaches the same: for, because the King Jeroboam was an idolater, the greater part of his kingdom began directly to worship idols, Cf. III Kings; and after the coming of Christ, during the reign of Constantine, the Christian Faith flourished; during the reign of Constantius, Arianism flourished; during the reign of Julian, Ethnicism again flourished; and in England, in our times, during the reign of Henry and, later, of Edward, the whole realm apostatized in a way; during the reign of Mary, the whole realm again returned to the Faith; during the reign of Elizabeth, Calvinism again became dominant, and the true religion went into exile.
But Christians are not obliged, indeed they ought not, in the face of a clear danger to religion, to tolerate an infidel king. For, when the divine right and human right are in conflict, the divine right must be observed to the disregard of the human: it is by divine right, however, to save true Faith and religion, which are one not many; it is by human right, however, that we have this or that King.
Finally, why cannot a Faithful people be freed from the yoke of an infidel King who is drawing others to Infidelity, if a Faithful spouse is free from the obligation to remain with an infidel spouse, when the latter does not want to remain with a Christian spouse without injuring the latter’s faith, as Innocent the Third deduces (in the chapter “Gaudeamus”, extra de divort.) from the First Letter of Paul to the Corinthians, chapter VII [the “Pauline Privilege” of marriage annulment]. For the right of one spouse over the other is not less than the right of a king over his subjects, but even somewhat greater.
A fourth reason: When kings and princes come to the Church to become Christians, they understand by an express or tacit pact that they subject their scepters to Christ and promise that they will preserve and defend the Faith of Christ, even under the penalty of losing their kingship; therefore, when they are heretics or are opposed to religion, they can be judged by the Church and even deposed from their kingship, nor will there be any injury to them if they are deposed. For one is not fit for the Sacrament of Baptism, who is not prepared to serve Christ and for His sake to lose whatever he has; for the Lord says in Luke, XIV, 26: “If anyone comes to me who does not ‘hate’ father or mother, spouse, and children, and even his own soul, he cannot be my disciple.” Moreover, the Church would err very seriously if it should admit any King who would wish without impunity to foster any sect whatever, and defend heretics, and overturn religion.
A fifth reason: When the Lord said to Peter, “Feed my sheep,” all power was given to him which is necessary for a Pastor: but a triple power is needed by a Pastor, one relating to wolves, in order that he may guard against them in every possible way; a second relating to rams, so that when they injure the flock with their horns, he can exclude them and prevent them from any longer going ahead of the flock; a third power over the rest of the sheep, that he may give to each of them suitable fodder; therefore, the Supreme Pontiff has the above threefold power.
Hence, three arguments may be adduced from this consideration; the first is, that the wolves that ravage the Church of God are heretics, as is clear from the passage of Matthew VII, 15: “Beware of false prophets etc.” Therefore, if some ruler from having been a lamb or a ram becomes a wolf, that is, from being a Christian he becomes a heretic, the Pastor of the Church can guard against him by excommunicating and by ordering the people not to follow him; and in this way deprive him of dominion over subjects.
A second argument can be: A shepherd can separate and isolate wild rams that are destroying the flock: A ruler, however, is a wild ram when, though Catholic in faith, he is sufficiently evil that he is a great obstacle to religion and the Church, as by selling bishoprics, confiscating churches, and such like activity. Therefore the Pastor of the Church can isolate him or reduce him to the level of a sheep.
A third argument is: A Shepherd can and should feed his sheep in a way suitable to them; therefore, the Pontiff can and ought to command and oblige Christians to observe those things that each of them is obliged to do, that is, to oblige them to serve God in the way that they ought, according to their station in life.
Kings, however, ought to serve God by defending the Church and punishing heretics and schismatics, as Augustine teaches (in epistle 73, ad Leonem Augustum), and Gregory (lib. II, ep. 61, ad Maurit.). Therefore, he can and ought to command Kings to do these things, and if they do not act, to oblige them under the pain of excommunication, and by other suitable means. Read the many observations of Nicholas Sanders (in Lib. II, cap. 4, on the Visible Monarchy) where you will find many of the points we have made.