Joseph Ratzinger, 1998:
This sheds light once again on “spiritual” [geistlich] office in the Church and on its theological location, which the tradition has defined with the term successio apostolica. “Apostolic succession” means precisely the opposite of what it might appear to mean, namely, that through the continuous chain of succession we become as it were independent of the Spirit. Linking to the line of succession in fact means that the sacramental office is never simply at our disposal, but must be given each time by the Spirit, that it is precisely the spirit-sacrament, which we can neither create nor institute ourselves. Functional competence as such is not by itsel sufficient for that, the Lord’s gift is necessary. In the sacrament, in the Church’s representative, symbolic action, the Lord reserves to himself the permanent institution of the priestly ministry. The totally specific combination of “once” and “always” characteristic of the mystery of Christ appears very beautifully here. The “always” of the sacrament, the presence of the historical origin in every age of the Church, implies a link with the ephapax, with the event of the origin that happens once only. This link with the origin, this stake planted in the ground of the once-only and unrepeatable event, is nonnegotiable. We can never take refuge in a free floating pneumatology, we can never leave behind the ground of the incarnation, of God’s action in history. But the converse is also true. This never-to-be-repeated event imparts itself in the gift of the Holy Spirit, who is the Spirit of the risen Lord. It does not vanish, like something dead and gone, into the forever irretrievable past, but has the force of the present, because Christ has passed through the “curtain, that is, through his flesh” (Heb 10:20: RSV) and has thereby released what endures forever in what takes place only once. The incarnation does not stop with the historical Jesus, with his “sarx” (2 Cor 5:16!). The “historical Jesus” has eternal significance precisely because his flesh is transformed in the resurrection, so that he can make himself present to all places and all times in the power of the Holy Spirit, as the farewell discourses in John wonderfully show (cf. especially Jn 14:28: “I go and I come to you”: RSV).
(Ratzinger, "Theological Locus," p 485-6.
Large text for emphasis is mine)