St Paul unequivocally teaches that the Church is a body. "Now if the Church is a body it must be something one and undivided, according to the statement of St Paul: ‘We, though many, are one body in Christ’ (Rom 12:5). And not only must it be one and undivided, it must also be something concrete and visible, as our Predecessor of happy memory, Leo XIII, says in his Encyclical “Satis Cognitum”: ‘By the very fact of being a body the Church is visible.’ It is therefore an aberration from divine truth to represent the Church as something intangible and invisible, as a mere ‘pneumatic’ entity joining together by an invisible link a number of communities of Christians in spite of their difference in faith.
“But a body requires a number of members so connected that they help one another. And, in fact, as in our mortal organism when one member suffers the others suffer with it, and the healthy members come to the assistance of those who are ailing, so in the Church individual members do not live only for themselves but also help one another, alleviating their suffering and helping to build up the entire body” (Pius XII, “Mystici Corporis”, 7).
“He is the beginning, the first-born from the dead”: this can be said because he was the first man to rise from the dead, never again to die (cf. 1 Cor 15:20; Rev 1:5), and also because thanks to him it enabled men to experience resurrection in glory (cf. 1 Cor 15:22; Rom 8:11), because they are justified through him (cf. Rom 4:25).
So, just as the previous verses looked to Christ’s pre-eminent role in creations the hymn now focuses on his primacy in a new creation—the rebirth of mankind, and all creation in its train, in the supernatural order of grace and glory. Christ rose from the dead to enable us also to walk in newness of life (cf. Rom 6:4). Therefore, in every way Jesus Christ is “pre-eminent.”
19. The word “pleroma” translated here as “fullness”, has two meanings in Greek: one, an active meaning, describes something that “fills” or “completes”; for example, a ship’s full load can be referred to as its “pleroma”. The other meaning is passive, “that which is filled” or “that which is complete”, so that a ship can be said to be “pleroma” when it is fully loaded. In this passage St Paul is using the word in both senses: Christ is the fullness (passive sense) of the Godhead (cf. Col 2:9), because he is full of all the perfections of the divine essence; and he is the fullness (active sense), because he fills the Church and all creation.
St John Chrysostom suggests that “the word ‘fullness’ is to be taken to mean the divinity of Jesus Christ …]. This term has been chosen the better to show that the very essence of the godhead resides in Jesus Christ” (“Hom. on Col, ad loc.”).
Since Christ possesses the divine nature, he also possesses the fullness of the supernatural gifts, for himself and for all mankind. Hence St Thomas’ comment that pleroma “reveals the dignity of the head in so far as it has the fullness of all grace” (Commentary on Col, ad loc.). In this sense, Christ is the fullness of the Church, for as its head he vivifies his body with all kinds of unmerited gifts. Finally, the entire created universe can be termed the “fullness” (“pleroma”) of Christ, because everything that exists in heaven and on earth has been created and is maintained in existence by him (cf. vv. 16-17); they are ever-present to him and are ruled by him (cf. Is 6:3; Ps 139:8; Wis 1:7; etc.). Thus, the world, which was created good (cf. Gen 1:31) tends towards its fulfillment insofar as it clearly reflects the imprint God gave it at the start of creation.
20. Since Christ is pre-eminent over all creation, the Father chose to reconcile all things to himself through him. Sin had cut man off from God, rupturing the perfect order which originally reigned in the created world. By shedding his blood on the cross, Christ obtained peace for us; nothing in the universe falls outside the scope of his peace-giving influence. He who in the beginning created all things in heaven and on earth has reestablished peace throughout creation.
This reconciliation of all things, ushered in by Christ, is fostered by the Holy Spirit who enables the Church to continue the process of reconciliation. However, we will not attain the fullness of this reconciliation until we reach heaven, when the entire created universe,
along with mankind, will be perfectly renewed in Christ (cf. “Lumen Gentium”, 48).
"The history of salvation–the salvation of the whole of humanity, as well as of every human being of whatever period–is the wonderful history of a reconciliation; the reconciliation whereby God, as Father, in the Blood and the Cross of his Son made man, reconciles the world to himself and thus brings into being a new family of those who have been reconciled.
"Reconciliation becomes necessary because there has been the break of sin from which derive all the other forms of break within man and about him. Reconciliation therefore, in order to be complete, necessarily requires liberation from sin, which is to be rejected in its deepest roots. Thus a close internal link unites “conversion” and “reconciliation”. It is impossible to split these two realities or to speak of one and say nothing of the other (John Paul II, “Reconciliatio Et Paenitentia”, 13).
Jesus Christ also counts on the cooperation of every individual Christian to apply his work of redemption and peace to all creation. The founder of Opus Dei says, in this connection: “We must love the world and work and all human things. For the world is good. Adam’s sin destroyed the divine balance of creation; but God the Father sent his only Son to reestablish peace, so that we his children by adoption, might free creation from disorder and reconcile all things to God” (“Christ Is Passing By”, 112).