The case for candidates being received at the Vigil:
563. Inclusion at the Easter Vigil of the rite of reception into full communion may also be opportune liturgically, especially when the candidates have undergone a lengthy period of spiritual formation coinciding with Lent.
This is the best argument, I’d say. The RCIA promotes the inclusion of the long-standing members of the faith community in the spirit of the initiation journey. There is a recognition that evangelization and initiation ministry develop not only the missionary sense of the faithful, but actually feed their faith. And if this is true for full members of the community, why not for those baptized in other traditions making the journey too? After reminding us of the preeminence of the Easter Vigil for the elect …
Candidates for reception, who in baptism have already been justified by faith and incorporated into Christ (Unitatis Redintegratio 3), are entering fully into a community that is constituted by its communion both in faith and in the sacramental sharing of the paschal mystery. The celebration of their reception at the Easter Vigil provides the candidates with a privileged opportunity to recall and reaffirm their own baptism, “the sacramental bond of unity [and] foundation of communion between all Christians.” (Unitatis Redintegratio 22).
Confirmation, after all, is “intimately connected with baptism.” And given the connection of Baptism with Eucharist, the rite emphasizes:
(T)he baptismal themes of the Easter Vigil can serve to emphasize why the high point of the candidates’ reception is their sharing in the eucharist with the Catholic community for the first time (see RCIA 475, no. 1).
