Whenever I teach a course in systematic (or dogmatic) theology, no matter the topic, I prefer to begin with an overview of the major components of the faith and how they all relate together. I do this because I believe it is important to see the part in light of the whole.
This brings me to the meaning of the term 'catholic' itself. Many people already know that the word 'catholic' comes from Greek and has the connotation of 'universal.' That is true, but that is not the only connotation. The original Greek word means something like: whole, integral, containing all essential elements in their proper relation. All the various doctrines of the faith are related to one another. They are not isolated questions; they are all part of one unified mystery.
Showing the unity of these topics should suffice to make the point: the Trinity, Creation (including Man), the Fall/Sin, the Incarnation & Redemption (Christology & Soteriology), the Church, the Sacraments, the Moral Life, and Eschatology (the last things). This is no mere notional unity; it is ontological unity, real unity. The leitmotif running through all of them is 'communion.'
The foundation of this unity is the Trinity. God is also the goal of everything. He is the origin and the end, the beginning and the end, the Alpha and the Omega. All things proceed forth from God, and all things find their fulfillment in God. The revelation that God is not a monad but a Trinity of Persons–one Divine Nature subsisting in three Divine Persons–has vast implications for our understanding of theology and reality as a whole.
It is a major corrective and complement to the thought of ancient Greek philosophers like Plato and Aristotle, who conceived of God as being a relationless monad. In reality, however, in his intra-Trinitarian life, God is the perfect loving communion of Three divine Persons. Thus, unity-within-distinction is the very basis and perfection of all existence. Relation is divine, and the communion of the Trinity is the source and goal of all reality.
This brings us to Creation. God creates in order to enable creation to share in His own goodness. In a particular way, with the creation of humanity, God makes creation capable of knowledge and of love by installing man with an intellect and a will. Thus, man is made in God's own image, imbued with the ability to know and to love. As an added reflection of this, God made man to be incomplete without relation to an other: male and female He created them. Thus, within human nature itself, there is the hallmark of inter-relatedness, of an orientation towards the intimate union of those who remain distinct but are united as one: 'and the two become one flesh.' Inter-personal relation, which has its origin in the Triune God, is thus reflected in human nature itself.
Yet, God does not force Himself on us. Like a would-be bridegroom, he proposes and invites, He does not coerce. Therefore, before the union between God and man can be complete, man must say 'yes' to the union. If the yes is not freely given then no true covenant–no real union–can be established. Without assent there is no authentic marriage.
Enter sin. The radical 'no' of sin represents a departure from God as well as from truth, goodness, and beauty. Since God is a relation of persons, the result of the rejection of God is the breaking of relationships. This happens on at least three levels. Sin leads to the division of man from God, of people from one another (human division), and even from within a single man (disintegration within oneself). Thus, sin has separated us from God, form one another, and even from ourselves. Within the depths of our own individual beings, there is a dis-integration: our bodies war against our souls, our appetites and desires threaten to control our choices against what we know; our intellects and our wills work in conflict rather than in concert. If man is to be redeemed, saved, all three levels must be restored and elevated to a new, higher level. Salvation must involve a complete and total union of man with God, humans with one another, and each individual human person within himself or herself.
Enter Christ. Man cannot redeem himself. He already owes everything to God. Thus, simply saying "I'm sorry" does not make up for the damage done. Man himself would not be happy without the insult to God being overcome by something greater than what was perpetrated (cf. St. Anselm of Canterbury). In order for man to be saved, it requires divine power and merit and yet also human payment. Even more than that, human nature itself must be renewed from within (cf. St. Athanasius of Alexandria). To both ends, we have the Incarnation: God became man! As God, His dignity is infinite and His deeds have infinite weight or merit. As man, He can provide what no other can: an offering on behalf of us all that can fully satisfy justice and provide infinite grace! (By the way, the Incarnation itself required human cooperation and acceptance, otherwise, we can't have the Incarnation: thus the importance of Mary's complete and total 'fiat': 'let it be done unto me according to thy word!' Mary's yes reverses the 'no' of Eve and enables the total self-sacrifice of Christ as the new Adam to undo the selfishness of the first Adam.) Along with some theologians, I tend to believe that even if man had never sinned, the Incarnation would have happened anyway as the goal of all creation: the Incarnation is the unsurpassable event of God's union with man. And if God's union with man is the goal of creation, then the Incarnation is the ultimate instance and source of union between God and man: the hypostatic union of one Divine Person (God the Son) in two complete natures (Divine and human). That is Jesus Christ, without whom redemption is literally impossible.
The reestablishment of the vertical communion with man and God is the most important aspect of salvation. However, it is no the only aspect, and for a complete understanding of the saving work of Christ, one cannot overlook (as we sinful creatures often do) the communal and individual dimensions of salvation. Christ came to save man not only abstractly but concretely both as a common species and as individuals and not just one or the other! The three levels of separation must all be overcome. They flow from the reestablishment of communion between God and man, but they cannot end there. Complete salvation must manifest itself in the union of men with one another: the Church.
Many scriptural passages witness to this fact; we shall limit ourselves to just a few. First, in the story of Adam and Eve, eve is taken from the side of Adam such that Adam can say that "this one at last is bone of my bone and flesh of my flesh" and "the two become one." On the cross, from the side of Christ pour forth water and blood, which are references to baptism and the Eucharist: two of the sacraments of initiation that incorporate one into the Church, which is the bride of Christ! The Church, in the New Testament, is referred to as both the body of Christ and as the bride of Christ. This should be understood nuptially. The Church and Christ remain distinct and yet somehow inseparable, just like man and woman become one flesh. Christ is the head of the body, the Church. St. Paul in his letter to the Ephesians makes this very clear. In his First Letter to the Corinthians, he also makes it very clear that this union as the body of Christ–the Church–takes place through the reception of the most Holy Eucharist: "The cup of blessing that we bless, is it not a communion [koinonia] in the blood of Christ? The bread that we break, is it not a communion [koinonia] in the body of Christ? Because the loaf of bread is one, we though man, are one body, because we all partake of the one loaf" (1 Cor 10:17). This led the great theologian Henri de Lubac to state: "the Eucharist makes the Church!" It is the common reception of the Most Holy Body and Blood of Christ in the Eucharist that effects the supernatural unity that is the Body of Christ, the Church. Akin to a marriage, the reception of the Eucharist–Holy Communion–is the consumation of the sacrament that is the Church! We receive Christ's body and thus become Christ's body after the manner of a bride becoming one with her husband. The two become one flesh! They are now inseparable. Furthermore, in John 17, we have perhaps the most heartfelt prayer of Jesus in the entire New Testament, when He prays: "That they may be one, as You and I are one" (John 17:22) He prays that the Church may not be divided but remain united "so that all may believe in me through their word" (verse 20). This reveals schism as a direct sin against the prayer and will of Christ Himself. It is an intolerable act of disobedience and of the dis-integration of the body of Christ.
And to this one Church that Christ instituted Himself, Christ gave the sacraments, which are individual instances in which His grace is conveyed in various ways for various purposes. They bring us into communion with one another and restore our personal integrity. They give us the grace necessary to live holy lives. Since morality is, at bottom, right relationship with God and others, even morality is tied to the concept of communion.
In turn, our moral lives here on earth are ordered towards our sanctification as individuals and as a community so that we can progress on the path to the salvation enjoyed by the Communion of Saints in Heaven (Eschatology), in which all are brought together in unity with one another through union with God, irrevocably and forever. If salvation–if heaven–is a share in divine life, and if divine life is communion, then heaven is communion: communion with God and with all the saints.
It is now, obvious, then, that these areas of doctrine are all connected. They are parts of one grand mystery of truth. God is the origin, the end, and the key for understanding all of them. His trinitarian communion is the source and goal of everything–everything in our faith and everything in reality. God is all in all!
