Laudatur Iesus Christus.
I hope the following is helpful, though I acknowledge it starts at a place where not everyone is willing to begin. (This is a recent effort on my part; I will be grateful for any help in discerning its faults and testing its joints.):
The Blessed Trinity is one God, in three persons: Father, Son, and Holy Spirit.
God is love.
Beginning with these, I think the following account makes sense of the other truths of Revelation:
All of creation is a gift from the Father to the Son. The Father wills that His gift please and serve His Son. When true to its nature, every creature pleases the Son. In turn, the Son loves His Father and wills that all things be dedicated to the service and delight of the Father. This mutual, total donation is the love, which is the life and being of the Trinity.
Human nature entails an especially delightful expression of honor for the Son: freewill.
When tempted, man chose not to serve freely as an instrument of the Father’s love. This decision to sin – to separate human will from God’s will – contradicted human nature at its roots; it destroyed man’s integrity and peace; and had two inevitable fruits: suffering and death.
Both fruits of man’s choice were offensive to God; they established a separate sphere of action and intent, expressing neither the Father’s love for the Son or the Son’s love for the Father. In this sense, Adam’s choice severed man’s life from the life of the Trinity. (“Grace” is a term for “the life of the Trinity;” hence, we say, ‘man fell from grace.’)
Once fallen, man could not recover. On his own, the best man could offer to God were expressions of man’s love. The best forms of this human love were symbolic imitations of the Trinity’s life; they could imitate and parallel, but they could never actually be conduits of love between persons of the Trinity.
To picture this think of two men: The first takes a note from a lover to his beloved. This man is a messenger, an agent of the lovers, freely serving communication between them. Imagine the second man declines to accept the lover’s note and rather writes one himself. When the second man delivers his note to the beloved, though it imitate and accurately symbolize the lover’s regard for the beloved, it cannot be a message from the lover to the beloved. Because the second man declined to be an agent of the lover, the link between lovers does not pass through him. Nothing the second man can do can change this.
Having removed man from the flow of Trinitarian love – from grace – Original Sin had other consequences for man: the contradiction between man’s will and his nature fractured man within himself. Man lost his ability to act with integrity. Because of this, even man’s attempts to love God became diffuse and halfhearted. This had broad ramifications: While even the best human effort could not return a man to grace, most men did attempt the best. Most men’s choices diverged more and more from God’s will. The separation of man’s will from God’s – sin – grew and spread, and with it: suffering.
This is the unredeemed world: Man’s will is severed from God’s and does not serve the loving purpose of creation. God’s will is frustrated by man, because man’s innovations, sin, suffering, and death, do nothing to express God’s love either for the Son or for man. Man is trapped in a world separate from grace and he cannot save himself.
This is the fractured state the Father willed the Son to heal.
The Son took on humanity. He freely accepted suffering and death, as an act of love and obedience to the Father. Only this could convert man’s offenses against God’s love into expressions of the love of the Son for the Father. Only a person of the Trinity could do this. By adopting suffering and death as expressions of His love for the Father, the Son redeemed them and admitted them into the stream of self-donation within the Holy Trinity. By this same act of submission and love, the Son accepted the necessary fruits of sin as instruments of His own will, bringing them into compliance with the Father’s will that all things belong to and serve the Son. By Christ’s death on the Cross, suffering and death were “redeemed” and became conduits of grace.
He took the consequences of our sins onto Himself, and thus saved the world.
Since the birth of the true Israel, man has been able to become a gift to the Son, in fulfillment of the Father’s will. Since the Crucifixion, man has been able to join his sufferings to Christ’s and thus allow them to be changed from an offense against God’s will into an expression of Christ’s love. Since the institution of the Holy Mass, by the grace of Christ, man can offer himself, his joy, and his suffering as acceptable offerings to God. Thus men have again been given the opportunity to freely render to God the obedience of sons rather than the compliance of slaves.
Gloria in altissimis Deo.