In the historical argument for the transitional diaconate, we noted that the grades of Holy Orders have, from the beginning and always, been received in a "cumulative and sequential" manner. Even when grades (either minor or major) were skipped, this remained true - there is zero evidence that anyone anywhere was ever ordained to the diaconate after the priesthood, or the subdiaconate after the diaconate, etc., even if that grade had previously been skipped. This is important, because it shows that the apostolic pattern has been maintained always and everywhere, even if some of the details of which orders are included, and which not (cantors, catechists, gravediggers, deaconesses, etc.), took more time to decide. Thus, the standard hierarchy of four minor orders (porter, lector, exorcist, acolyte) and four major orders (subdeacon, deacon, priest, bishop) became fixed for the Latin Church even as early as the third century, and were invariably received in this order by roughly 700.
This apostolic pattern in favor of the transitional diaconate is also supported by two potent theological arguments. One is the "sacra potestas" argument. The other, which we won't broach in this post, is the unity of the sacrament argument.
We'll briefly look at the sacra potestas argument in five questions.
1. What is a "sacra potestas?" A sacra potestas is a "sacred power," that is, a piece of Christ's own divine power, given explicitly to the Apostles, and passed on by them to their successors and helpers by the laying on of hands and (eventually) the precise ritual of ordination to each grade.
These "sacred powers" are obviously rather important, because they are precisely that for which Christ gave us the sacrament of Holy Orders. At the very least, He willed the Church to have bishops to rule, to confirm, and to ordain; priests to confect the Eucharist and to forgive sins; and deacons to proclaim the Gospel. And, given what the Magisterium of the Church is in fact, we must also admit that the subdiaconate and the minor orders also were part of what He willed, at least for the temporality of the Church, if not for her divine constitution (i.e., they are consistent with the will of Christ, but not constituent of it, as bishops, priests, and deacons are).
The hierarchy of "sacred powers," then, is the essence, the "what," of Christ's divine ministry carried out by the Church. It guides how the sacraments are poured out for the people. It defines what is and is not "ecclesial" and "secular," in their particular spheres of human activity (see St. Augustine's "City of God," or Pope Gelasius's "two swords" doctrine, etc.). And it fundamentally shapes the pastoral care of the Church, without defining the "how" of that care dogmatically.
2. Does every grade have a "sacra potestas?" All the major orders have a sacred power. The ordination rites of the Latin Church - I'm looking at those used from roughly 700 until the reforms of Vatican II - were extremely clear about the power given to each grade, both in the words used, and in the symbols. (The current rites have shifted emphasis away from the powers of each grade, and so are not nearly so clear about them.) The power was explicitly conveyed, usually with the formula "Receive the power of... (Accipe potestatem...)" according to each grade.
Moreover, the sacred powers of the bishop and of the priest were clearly and dogmatically defined by the Magisterium, most coherently at Trent (especially Session XXIII), but not uniquely at that Council. Bishops have the fullness of the Holy Spirit, the apostolic power of governance of the Church, and the power to confirm and to ordain. In the ordination rite, the bishop-elect was ordained when the consecrating bishops each put their hands on his head and said, "Receive the Holy Spirit." The other powers were enumerating in the signs of the rite: chrismation of the hands, giving of the pastoral staff, ring, and miter, and giving of the Gospels (apostolic commission).
Priests have the power to confect the Eucharist "in persona Christi," and to absolve from sins (Confession and Anointing). In the ordination rite, the newly ordained priest was then told, "Receive the power to offer the sacrifice to God, and to celebrate Masses, as much for the living as for the dead."
The exact sacred power of the deacon (or the subdeacon) has never been dogmatically defined with this same precision. But it is dogmatic that the deacon has sacred power (Trent, Session XXIII, chapter 4; Lumen Gentium 18), and this has always been understood of the subdeacon, too, although not to my knowledge asserted dogmatically. Major Orders convey powers, and the lex orandi is the lex credendeni. Thus, what is true of bishop and priest in the ordination rite is also true of deacon (and subdeacon) in the same rite.
3. What is the deacon's "sacra potestas?" This has never, as far as I know, be dogmatically defined. However, for more than twelve centuries, every deacon ordained in the Latin Church was told, "Receive the power of reading the Gospels in the Church of God, as much for the living as for the dead." Nor is there any other tradition about the deacon's sacred power floating around out there. The Church has always believed, then, and expressed clearly in her lex orandi, that the deacon's sacred power is to proclaim the Gospel within the Church.
This is why reading the Gospel is the deacon's characteristic function within the Church's liturgy. This function is the most immediate manifestation of the deacon's sacred power, in exactly the same way that presiding at Mass and offering Confession and Absolution are the most immediate manifestations of the priest's sacred power. It should be noted, however, that while the priest always exercises his sacred power "in persona Christi," such that it is in fact Christ who changes bread and wine into His own Body and Blood, and Christ who says, "I absolve you...," there's no parallel tradition of the deacon acting "in persona Christi."
The other parts of the deacon's ministry, of sacrament and of charity, relate to the proclamation of the Gospel in fairly direct ways. The Gospel is at the root of all the Church's teachings, so catechesis and sacramental preparation are derivative forms of proclaiming the Gospel. Baptism is the beginning of receiving the Gospel in the Church, so deacons can baptize (e.g., Philip and the Ethiopian eunuch). The Gospel must be proclaimed in action as well as by words, so deacons "sacramentalize the service of the Church," as Pope John Paul II put it.
Again, this is exactly parallel to how the other parts of a priest's ministry relate to the Eucharist (e.g., Lumen Gentium 28 - see more below); and to how the various parts of a bishop's ministry in the "fullness of orders" fit together in the three-fold responsibility to govern, sanctify, and teach.
4. Where in the Gospel does Christ give the Apostles such a power? Lk 9:1-6 is the most clear (parallel passages in Mt 10 and Mk 6). The Twelve receive the power to "keryssein" (preach, herald), and they went out "euaggelizomenoi" ("gospelizing," proclaiming the Gospel or coming of the Kingdom). Luke is most interesting on this point, because in Lk 10, he recounts a separate commission for the 72 disciples, with a different vocabulary of what exactly they are commissioned to do. They are not given a power ("dynamis"), but told only to "say" ("legete," 10:8) the Kingdom is coming.
This same power to "kerygein" the "kerygma," and to "euaggelizein," that is, to proclaim the Good News, is precisely what is given by the Twelve to the Seven in Acts 6, by the laying on of hands. Philip, using this gift of sacred power, explicitly "kerygein-ed" Christ to the Samaritans (8:5), many of whom were healed of demons and baptized; and "euaggelizein-ed" Christ to the eunuch (8:35), who was also baptized. Stephen's trial before the Sanhedrin is unmistakably a "kerygma," completed in his martyrdom (baptism of blood), which led directly to the conversion of the witness Saul.
5. How does this defend the transitional diaconate? The end of the deacon's proclaiming the Gospel, in every ministerial context, is the relationship of the hearer with Christ. In the case of initial conversion, that means baptism first; in the case of the baptized, it means the Eucharist. Deacons proclaim in order to bring people to Christ, and the deepest union with Christ in this life is the Eucharist.
The wisdom of the Tradition is that proclaiming leads to deeper union with Christ. Priests also have the power of proclaiming, in order to make their ministry of uniting and reconciling (Eucharist and absolution) more accessible and more fruitful. The one leads naturally to the other. (This is as it must be, if there is in fact one priesthood of Christ in the New Covenant; but we needn't get into the unity argument here.)
Lumen Gentium 28 states most clearly the theological relationship of the power of proclaiming to the power of confecting and absolving, in the ministry of priests:
By the power of the sacrament of Orders, in the image of Christ the eternal high Priest, they are consecrated to preach the Gospel and shepherd the faithful and to celebrate divine worship, so that they are true priests of the New Testament. Partakers of the function of Christ the sole Mediator, on their level of ministry, they announce the divine word to all. They exercise their sacred function especially in the Eucharistic worship or the celebration of the Mass by which acting in the person of Christ and proclaiming His Mystery they unite the prayers of the faithful with the sacrifice of their Head and renew and apply in the sacrifice of the Mass until the coming of the Lord the only sacrifice of the New Testament, namely that of Christ offering Himself once for all a spotless Victim to the Father. For the sick and the sinners among the faithful, they exercise the ministry of alleviation and reconciliation and they present the needs and the prayers of the faithful to God the Father.
To be true priests of Christ, both in His image and "in persona," priests must preach the Gospel, shepherd the people to Christ, and celebrate the sacraments. They cannot mediate like Christ the Mediator without announcing the Gospel. They cannot unite the faithful to the sacrifice of the altar without proclaiming the mystery of Christ's death and resurrection. This is simply what it means to be a priest of Jesus Christ.
If, however, priests were not ordained deacons first, then they would never receive the sacred power of proclaiming. Like the 72 disciples, they would be able to "say" the Kingdom, but not "proclaim" it with "power and authority." The healing sacraments would be disconnected from the Word, quite contrary to what Luke clearly says in 9:1-6, or what the Church has clearly stated in LG 28. They would not be able to preach in the same ministerial acts as shepherding and celebrating; they would not be able to mediate like Christ, and they would not be able to unite the faithful to the sacrifice of the altar.