The following is an excerpt from An Exposition of the Westminster Confession of Faith by Robert Shaw.

There is no other head of the Church but the Lord Jesus Christ. Nor can the Pope of Rome, in any sense, be head thereof; but is that Antichrist, that man of sin, and son of perdition, that exalts himself, in the Church, against Christ and all that is called God (WCF 25.6).

Exposition

That the Lord Jesus Christ is the alone head of the Church must be maintained, not only in opposition to Papists, who affirm that the Pope of Rome, as the successor of Peter and the vicegerent of Christ, is the head of the universal Church; but also in opposition to Erastians, who make the supreme magistrate the head of the Church within his own dominions.

A universal headship or dominion belongs to Christ. As God, he has a natural and essential right to rule and dispose of all creatures at his pleasure, and for the manifestation of his own glory. As Mediator, he has a universal headship by donation from the Father. It is said (Eph. i. 22), the Father “gave him to be the head over all things to the Church;” where, it is to be observed, the apostle is not treating of Christ’s headship over the Church, but of his universal headship as Mediator. He is constituted head “over all things;” but this power is delegated to him that he may overrule all things for the good of the Church; and therefore he is said to be head “over all things to the Church,” or for her benefit.. But Christ has a peculiar headship over the Church, which is his body. This is expressly asserted (Col. i. 18): “He is the head of the body, the Church.” Here he is compared to the head of the natural body; and in Eph. v. 23, he is declared to be the head of the Church, as the husband is the head of the wife.

To the visible Church Christ is a head of government and direction. He is the “Ruler in Israel,” and “the government shall be upon his shoulder.”—Isa. ix. 6. “Yet have I set my King,” says Jehovah, “upon my holy hill of Zion.” Ps. ii. 6. To him it belongs to enact laws for his Church —to institute the ordinances of worship, and the form of government to be observed by her—to appoint her office-bearers, and to prescribe the manner of their admission into office. To the Church invisible Christ is not only a head of government and direction, but also of vital influence. Hence he is called “the head, from which all the body, by joints and bands, having nourishment ministered, and knit together, increaseth with the increase of God.”—Col. ii. 19. Christ is the sole and exclusive head of the Church, whether considered as visible or as invisible. His authority alone is to be acknowledged by the Church, as her supreme Lawgiver. Her language must ever be: “The Holy One of Israel is our king.” Let men distinguish as they will, but as a body with more heads than one would be a monster in nature, so the Scripture clearly shows that the body of Christ, which is the Church, is no such monster. As there is “one body,” so there is only “one Lord.” Christ has not delegated his authority either to popes or princes; and though he is now in heaven as to his bodily presence, yet he needs no depute to act for him in the Church below. Before he ascended up on high, he gave this precious promise to his disciples: “Lo, I am with you alway, even unto the end of the world:” and “where two or three are gathered together in his name, there he is in the midst of them.” – Matt. xxviii. 20, xviii. 20.

Daring encroachments have been often made upon this royal prerogative of Christ, both by ecclesiastical and civil powers. Long has the Man of Sin and Son of Perdition blasphemously arrogated universal headship and lordly dominion; and when the Reformation took place in England, the headship over the Church was only transferred from the Roman Pontiff to the British Sovereign. Henry VIII. was recognised as “supreme head of the Church of England;” and it was enacted, “that the king, his heirs, &c., shall be taken, accepted, and reputed, the only supreme head on earth of the Church of England, called Anglicana Ecclesia; and shall have and enjoy, annexed and united to the imperial crown of this realm, as well the title and style thereof as all honours, dignities, immunities, profits, and commodities to the said dignity of supreme head of the said Church belonging and appertaining.” It was also enacted, that his majesty hath full authority to exercise “ecclesiastical jurisdiction;” and ” that the archbishops and bishops, have no manner of jurisdiction ecclesiastical, but by, under, and from the royal majesty.” In the commencement of Queen Elizabeth’s reign, the metaphorical term head was changed into supreme govenor; but both terms signify the same thing. No part of the power or authority which had been possessed by her royal predecessors was relinquished; for, at the same time, it was enacted, that “all jurisdictions—spiritual and ecclesiastical— should for ever be united and annexed to the imperial crown.” This sacrilegious usurpation of spiritual authority, and impious invasion of Christ’s sovereignty, is sanctioned by the Church of England, in her 37th Article. It runs thus: “The queen’s majesty hath the chief power in this realm of England, and other her dominions; under whom the chief government of all estates of this realm, whether they be ecclesiastical or civil, in all causes doth appertain.” Some Churchmen, indeed, seem to be ashamed of recognising the sovereign as head or supreme governor of the Church, and have attempted to palliate or explain away the real import of the title. But the attempt is vain; of the spiritual jurisdiction which the title involves, and of the Erastian bondage under which the Church of England is held, numerous proofs can be easily adduced. Who knows not, for example, that the appointment of all her bishops belongs to the sovereign—that her clergy cannot meet in convocation without the permission of her majesty; and that the convocation has actually been suspended, or virtually abolished, for upwards of a century? That a Church so completely fettered is utterly powerless for the suppression of heresy and for the exercise of discipline recent events have too clearly demonstrated.

The Church of Scotland, at the era of the Reformation, nobly asserted, and practically vindicated, the sole headship of Christ. This was especially the grand and leading principle of the Second Reformation; and it was in the way of contending for the royal prerogatives of Christ, as her alone king and head, and resisting the Erastian encroachments of aspiring princes upon her spiritual liberties, that many of her sons suffered bonds and exile, and shed their blood in fields and on scaffolds. Though the sole headship of Christ is explicitly asserted in our Confession of Faith, yet it is deeply to be regretted that this vital principle was not more effectually guarded in the Revolution Settlement. The Act 1592, upon which the Church was erected at this time, contained no acknowledgement of the headship of Christ; and it was not formally asserted by any act of the General Assembly. Though a regal supremacy was neither directly claimed by the Crown nor conceded by the Church, yet it was not long till it was virtually exercised. The meetings of the General Assembly were repeatedly dissolved and prorogued by the sovereign; and, in 1703, when the Assembly had prepared the draft of an act for the purpose of asserting the supremacy of Christ, the intrinsic power of the Church, and the divine right of the Presbyterian government, it was abruptly dissolved by her majesty’s commissioner, without any recorded protest. “But ecclesiastical independence was still more invaded, and spiritual interests more effectually subjected to secular dominion, by the restoration of the power of lay-patrons, after it had been repeatedly abolished. The power of patronage, when it is of any real effect in the settlement of the vacant churches, flows from the same spring with the ecclesiastical supremacy, and can neither be vindicated nor condemned, but on the same principles with it; and is indeed, when exercised by the Crown, a branch of it.” Without referring particularly to those recent struggles of the Church to vindicate her spiritual independence, which have issued in the disruption of the Scottish Establishment, there is nothing, it may be remarked, more clearly evinced by these events, than the determined resolution of the State to retain and exercise an Erastian power over the Church. But the Christian people of Scotland have given the most unequivocal proofs of their continued and firm attachment to the sole supremacy of Christ as “king in Zion”—a truth in defence of which their ancestors “loved not their lives unto the death.” They cannot contend or suffer in a nobler cause. Those who assume a headship over the Church of Christ, are guilty of an impious usurpation of his prerogatives; and his faithful subjects are bound to display their loyalty to him, by asserting his sole right to reign and rule in his own Church, and by giving no countenance to a claim so degrading to the Church, and so dishonouring to her alone king and head.