Why the ecclesial ministry?
Christ is himself the source of ministry in the Church. He instituted the Church. He gave her authority and mission, orientation and goal:
In order to shepherd the People of God and to increase its numbers without cease, Christ the Lord set up in his Church a variety of offices which aim at the good of the whole body. the holders of office, who are invested with a sacred power, are, in fact, dedicated to promoting the interests of their brethren, so that all who belong to the People of God . . . may attain to salvation.
“How are they to believe in him of whom they have never heard? and how are they to hear without a preacher? and how can men preach unless they are sent?” No one – no individual and no community – can proclaim the Gospel to himself: “Faith comes from what is heard.” No one can give himself the mandate and the mission to proclaim the Gospel. the one sent by the Lord does not speak and act on his own authority, but by virtue of Christ’s authority; not as a member of the community, but speaking to it in the name of Christ. No one can bestow grace on himself; it must be given and offered. This fact presupposes ministers of grace, authorized and empowered by Christ. From him, they receive the mission and faculty (“the sacred power”) to act in persona Christi Capitis. the ministry in which Christ’s emissaries do and give by God’s grace what they cannot do and give by their own powers, is called a “sacrament” by the Church’s tradition. Indeed, the ministry of the Church is conferred by a special sacrament.
Intrinsically linked to the sacramental nature of ecclesial ministry is its character as service. Entirely dependent on Christ who gives mission and authority, ministers are truly “slaves of Christ,” in the image of him who freely took “the form of a slave” for us. Because the word and grace of which they are ministers are not their own, but are given to them by Christ for the sake of others, they must freely become the slaves of all.
Likewise, it belongs to the sacramental nature of ecclesial ministry that it have a collegial character. In fact, from the beginning of his ministry, the Lord Jesus instituted the Twelve as “the seeds of the new Israel and the beginning of the sacred hierarchy.” Chosen together, they were also sent out together, and their fraternal unity would be at the service of the fraternal communion of all the faithful: they would reflect and witness to the communion of the divine persons. For this reason every bishop exercises his ministry from within the episcopal college, in communion with the bishop of Rome, the successor of St. Peter and head of the college. So also priests exercise their ministry from within the presbyterium of the diocese, under the direction of their bishop.
Finally, it belongs to the sacramental nature of ecclesial ministry that it have a personal character. Although Chnst’s ministers act in communion with one another, they also always act in a personal way. Each one is called personally: “You, follow me” in order to be a personal witness within the common mission, to bear personal responsibility before him who gives the mission, acting “in his person” and for other persons: “I baptize you in the name of the Father and of the Son and of the Holy Spirit …”; “I absolve you….”
Sacramental ministry in the Church, then, is at once a collegial and a personal service, exercised in the name of Christ. This is evidenced by the bonds between the episcopal college and its head, the successor of St. Peter, and in the relationship between the bishop’s pastoral responsibility for his particular church and the common solicitude of the episcopal college for the universal Church.
From the Catechism of the Catholic Church 874-879