Christ Alone is the Head of the Church
In the third part of the Summa theologica, St. Thomas Aquinas asks the question whether it is proper to Christ to be the Head of the Church and answers in the affirmative. Protestants often claim that the Catholic Church has set the pope as the head of the Church instead of Christ. But St. Thomas believes in the universal jurisdiction of the pope and also in the unique Headship of Christ over the Church. Likewise, Catholics are able to affirm the primacy of the pope without denying that Christ is the unique Head of the Church. St. Thomas says:
It is written (Colossians 2:19): “The head” of the Church is that “from which the whole body, by joints and bands being supplied with nourishment and compacted groweth unto the increase of God.” But this belongs only to Christ. Therefore Christ alone is Head of the Church.1
But how can St. Thomas affirm that Christ is the Head of the Church even while other men, especially the pope, are understood to be the head of the Church? St. Thomas answers in two ways. First because other men are called “head of the Church” in a limited sense whereas Christ is called ‘Head’ in the proper and fullest sense.
First, inasmuch as Christ is the Head of all who pertain to the Church in every place and time and state; but all other men are called heads with reference to certain special places, as bishops of their Churches. Or with reference to a determined time as the Pope is the head of the whole Church, viz. during the time of his Pontificate, and with reference to a determined state, inasmuch as they are in the state of wayfarers.2
The second reason St. Thomas gives is that Christ is called the Head of the Church by His own power and authority whereas other men are only called head of the Church because they are acting in Christ’s place. We call the general the head of the army but not to the exclusion of the king’s headship. The general takes the place of the king on the battlefield, but he does not replace the king as the ultimate head. When we call the general “head,” we do not deny the headship of the king. We do not deny Christ as the true Shepherd when we say that pastors ‘shepherd’ their flocks, and neither do we deny His Headship by calling other men ‘head’ in a limited sense. St. Thomas writes:
Secondly, because Christ is the Head of the Church by His own power and authority; while others are called heads, as taking Christ’s place, according to 2 Corinthians 2:10, “For what I have pardoned, if I have pardoned anything, for your sakes I have done it in the person of Christ,” and 2 Corinthians 5:20, “For Christ therefore we are ambassadors, God, as it were, exhorting by us.” 3
St. Thomas also quotes St. Augustine saying, “If the rulers of the Church are Shepherds, how is there one Shepherd, except that all these are members of one Shepherd?” St. Thomas concludes, “So likewise others may be called foundations and heads, inasmuch as they are members of the one Head and Foundation.”4