1. Let's start at the beginning. What is ultramontanism? The basic idea of the word, which literally means "beyond the mountains", is that the authority of the Roman Pontiffs extends beyond the Papal States and the suburbicarian dioceses of Rome, into Northern Europe and beyond.
2. Ultramontanism is a vague and relative term. For example, in the context of a discussion about whether the Pope has universal jurisdiction over the Church, the affirmative view would be called "ultramontane", even though this is not the definition of ultramontanism. The term has no precise definition in current usage. In general, whenever there are several viewpoints about the extent of papal power or authority, the one that maximizes that power or authority is labeled "ultramontane" relative to the other viewpoints.
3. The various forms of Christian piety surrounding the Pope go back a long way. One can find them already in the expressions of bishops in reference to the Roman Pontiff at the early ecumenical councils, and probably elsewhere beforehand.
4. The piety due to the pope is a special form of the piety due to all bishops. Bishops are our spiritual fathers; they have the fullness of the Christian priesthood; they hold the shepherd's crook and wear the signet ring; jurisdiction belongs to them, both as shepherds who work in place of the Good Shepherd, and as princes who reign in place of Christ the King. All of these things apply to the Roman Pontiff to a greater degree. He has supreme jurisdiction, and not merely local jurisdiction. He has care for the well-being of all the particular churches, and not just the Roman church. He is alter Christus more than any other priest on earth, even if his priesthood as such is not ontologically different from that of any other bishop, because of his hierarchical position within the body of Christ, and because of his role as guarantor of Christian unity.
5. Because the pope is a symbol of the unity of the faithful and possesses, by virtue of his universal jurisdiction and care of souls, a paternity with respect to all Christians, certain mistakes are easy to make. It is easy, especially for the lay faithful, who live mostly in the world and only occasionally within the Church, to think of the pope as the Church. And it is easy for everyone, because of his role as supreme lawgiver in the Church Militant, to think that everything the pope says and does is binding on all Catholics. Today especially, when the consideration of what has been handed down has been worn away almost to nothing, it is easy for everyone to think of the pope as the primary authentic source of doctrine and law.
6. Obviously the pope is a lawgiver, just as every bishop is, and in the Church Militant he stands above all the other bishops. But just as each bishop is merely a steward or vassal of a higher authority—one hired to tend the sheep or work in the vineyard—in the same way the pope himself is merely a steward or vassal. And just as any merely political ruler is subject in his decrees to the eternal law of justice and the natural order of human relations, in the same way the pope and other bishops are subject not just to the natural law, but also to the revealed law of God.
7. In one way we can look at the Roman Pontiff and say that he is more of an absolute monarch than almost any ruler remaining on earth. His authority is not subject to a constitution, or elections, or even the review of his peers. But this impression is misleading, because modern political authority is predominately conceived around a theory of legal positivism, according to which it is merely the act of the sovereign which makes laws, and the power of enforcement which makes them legitimate. Under such a conception, any law the ruler can get away with making is binding on his subjects. But not so with the pope or his bishops. As emissaries of a higher authority, as stewards of the Kingship of Christ, their authority, their status as authentic lawgivers, is hemmed in by the strictures of divine law. As a result, neither a pope nor any other bishop can speak with authority if he speaks merely for himself, nor can he simply legislate as he likes without care for the requirements of his office. The validity of the acts of the pope are profoundly limited by the divine mandate from which all priestly authority is derived.
(To be continued... a complete index of this series can be found here.)