Why was there a delay of eight years from Lumen Gentium to this motu proprio? The pope explains:
However, this restoration of the permanent diaconate required that the instructions of the Council be more profoundly examined and that there be mature deliberation concerning juridical status both of the celibate and married deacon Similarly it was necessary that matters connected with the diaconate of those who are to become priests should be adapted to contemporary conditions, so that the hire of diaconate would furnish that proof of life, of ministry and of aptitude for the priestly ministry, which ancient disciples demanded from candidates for the priesthood.
And we had the last motu proprio, SDO, which laid some of the groundwork in terms of norms and aspects to be determined:
Thus on 18 June 1967 we issued in motu proprio form, the Apostolic Letter Sacrum Diaconatus Ordinem, by which suitable canonical norms for the permanent diaconate were established. (AAS 59 (1967), pp. 697-704.) On June 17 of the following year, through the Apostolic Constitution Pontificalis Romani Recognitio, (AAS 60 (1968), pp. 367-373.) we authorised the new rite for the conferring of the sacred orders of diaconate, priesthood and episcopacy, and at the same time defined the matter and the form of the ordination itself.
Naturally, the pope wants deacons to know ahead of time what they are getting themselves into:
Now that we are proceeding further and are today promulgating the Apostolic Letter Ministeria Quaedam, we consider it fining to issue certain norms concerning the diaconate. We also desire that candidates for the diaconate should know what ministries they are to exercise before sacred ordination and when and how they are to take upon themselves the responsibilities of celibacy and liturgical prayer.
The diaconate ministries vary somewhat from diocese to diocese, and naturally, from deacon to deacon. Sometimes “good men” are discerned who fit well into some or many diaconate ministries. Sometimes lay people who have functioned well in ecclesial ministry have a sound discernment to continue and expand that ministry as a deacon.
The multiple preliminary stages into the priesthood have been abandoned, mostly. First tonsure is eliminated, and the diaconate, permanent or transitional, marks the entry point into the clergy:
Since entrance into the clerical state is deferred until diaconate, there no longer exists the rite of first tonsure, by which a layman used to become a cleric. But a new rite is introduced, by which one who aspires to the diaconate or priesthood publicly manifests his will to offer himself to God and the Church, so that he may exercise a sacred order. The Church, accepting this offering, selects and calls him to prepare himself to receive a sacred order, and in this way he is properly numbered among candidates for the diaconate or priesthood.
Some clarification on the role of lector and acolyte:
It is especially fitting that the ministries of lector and acolyte should be entrusted to those who, as candidates for the order of diaconate or priesthood, desire to devote themselves to God and to the Church in a special way. For the Church, which “does not cease to take the bread of life from the table of the word of God and the body of Christ and offer it to the faithful,” (Dei Verbum 21) considers it to be very opportune that both by study and by gradual exercise of the ministry of the word and of the altar, candidates for sacred orders should through intimate contact understand and reflect upon the double aspect of the priestly office. Thus it comes about that the authenticity of the ministry shines out with the greatest effectiveness. In this way the candidates accede to sacred orders fully aware of their vocation. fervent in spirit serving the Lord, constant in prayer and aware of the needs of the faithful. (Cf. Rom. 12:11-13.)
This concludes the unnumbered introduction to the motu proprio Ad Pascendum. In the next four posts (only 4!), we’ll cover the meat of the document: norms, ordination liturgy, requirements, etc.. Then we’ll head on to the ordination rites themselves.