The ecumenical service that the presbyter can provide is based on the very nature of his ministry of unity.

This unity does not derive from the practice of a human power, of which the hierarchical priesthood is assumed to be the expression. The presbyter is not the paradigmatic example of the Gospels substituted by human will and power, as claimed at the origins of the protestant reformation. Nor is it the expression of the natural religious dynamics of mankind, that would become endowed with associative forms and a functional, symbolic and intellectual organization.

The unity served by the presbyter is the one generated by the historical presence of Jesus Christ and the accomplishment of His mission. This unity precedes therefore any practice of the presbyterate and is founded on the presence of the Son of God made Man, and also upon His Gift of the reconciliation and communion of men in His name.

Hence the affirmation in which the presbyterial service is entered: the presbyter acts as a minister of Christ, in persona Christi, Who through him continues to sanctify, to teach and to guide mankind; so as to accomplish such a sublime service, the presbyter receives a particular gift from the Holy Spirit, passed on since the time of the apostles through the imposing of the hands. This ministry, for its very nature, can only be practiced in the hierarchic communion (see LG 21); therefore, the gift of the Spirit received is intrinsically directed towards serving the unique Gospels, that continue to act in the Word and the Sacraments of Christ and of the Church, so as to build it within the life of the Christian faithful.

Therefore it is possible to affirm that the presbyter can practice his ministry of unity only if he himself remains within the unity of the Church, united with his Bishop, who, in turn, is a member of that college which succeeded that of the apostles, lead by Peter’s successor. Hence, thanks to the structural dependence on Christ and on the Church, in virtue of which the presbyter dedicates himself to the work of the Other and not to the creation of a personal plan, he will always be aware of his being precisely a "minister", a "servant" of Christ, who continues to introduce mankind to Communion with His Body through the Holy Spirit.

The unity of Christ’s Church, that exists in the Catholic Church (see LG 8), therefore appears as a "place" of origin, and at the same time the mission to which the presbyter is called upon to dedicate his entire life, in the faithfulness and fruitfulness bestowed by the Holy Spirit. Consequently, ecumenism, the preoccupation for the fullness of visible unity among all the Christians belonging to other Churches or ecclesiastic Communities, cannot be considered as something extraneous or artificial as far as the presbyterial ministry is concerned, but rather an element that is eradicated within it, revealing its very essence.