The Problem: Our separated brethren deny that we can truly partake of the divine nature or, in the case of Mormons, they go to the other extreme and claim that each of the saved become completely divine, gods of their own worlds after death.
The Truth: Through the sacraments, founded in the blood of Jesus Christ, we partake of divinity. Though the inexpressible gulf between our humanity and God's divinity still exists and will exist through all eternity, we truly participate in the divine nature, each of us becoming not just a legal, but a real child of God.
When explaining divinization, Thomas Aquinas used the example of an iron poker heated in a fire. Though the red-hot poker never itself becomes fire, yet it participates in every characteristic of the fire. So do we participate in the divine nature through the perfection brought about in purgation and the sacraments. Through these active experiences of the Divine, we are filled to the capacity of our being with divinity.
Gen 1:27 So God created man in his own image, in the image of God he created him; male and female he created them.
Gen 5:1-3 This is the book of the generations of Adam. When God created man, he made him in the likeness of God. 2 Male and female he created them, and he blessed them and named them Man when they were created. 3 When Adam had lived a hundred and thirty years, he became the father of a son in his own likeness, after his image, and named him Seth....
We are made in the image and likeness of God. That image may have been marred by original sin, but it can be restored. It is brought to perfection through Jesus Christ in a way that simply was not possible in Adam, for the New Adam supersedes and perfects the old in a way not available to the first Adam, even if he had not fallen.
Mt 5:48 You, therefore, must be perfect, as your heavenly Father is perfect.
God commanded it, so it is literally possible. It can only be attained through participation in the divinity of Jesus.
Heb 12:23 and to the assembly of the first-born who are enrolled in heaven, and to a judge who is God of all, and to the spirits of just men made perfect...
Heb 10:14 For by a single offering he has perfected for all time those who are sanctified.
2 Pet 1:3-4 His divine power has granted to us all things that pertain to life and godliness, through the knowledge of him who called us to his own glory and excellence, 4 by which he has granted to us his precious and very great promises, that through these you may escape from the corruption that is in the world because of passion, and become partakers of the divine nature.
Scripture attests that we truly participate in the divine nature.
Jn 17:20-23 "I do not pray for these only, but also for those who believe in me through their word, 21 that they may all be one; even as thou, Father, art in me, and I in thee, that they also may be in us, so that the world may believe that thou hast sent me. 22 The glory which thou hast given me I have given to them, that they may be one even as we are one, 23 I in them and thou in me, that they may become perfectly one, so that the world may know that thou hast sent me and hast loved them even as thou hast loved me.
Col 2:9-10 For in him the whole fulness of deity dwells bodily, 10 and you have come to fulness of life in him, who is the head of all rule and authority
Col 1:26-27 the mystery hidden for ages and generations but now made manifest to his saints. 27 To them God chose to make known how great among the Gentiles are the riches of the glory of this mystery, which is Christ in you, the hope of glory.
This is possible because Christ truly resides in us, and we in Him, through the sacramental life.
1 Jn 3:1 See what love the Father has given us, that we should be called children of God; and so we are.
We are all made into firstborn children of God, truly made perfect as God is perfect before God through Christ. We are individually members of Christ's Body.
Gal 4:4-7 But when the time had fully come, God sent forth his Son, born of woman, born under the law, 5 to redeem those who were under the law, so that we might receive adoption as sons. 6 And because you are sons, God has sent the Spirit of his Son into our hearts, crying, "Abba! Father!" 7 So through God you are no longer a slave but a son, and if a son then an heir.
2 Cor 4:11 For while we live we are always being given up to death for Jesus' sake, so that the life of Jesus may be manifested in our mortal flesh.
Eph 2:15 by abolishing in his flesh the law of commandments and ordinances, that he might create in himself one new man in place of the two, so making peace...
God has only one Son. However, we are made one new man in place of the two, part of the Body of the Son, through the sacramental life. Thus, we become heirs with Christ.
Rom 8:14-17 For all who are led by the Spirit of God are sons of God. 15 For you did not receive the spirit of slavery to fall back into fear, but you have received the spirit of sonship. When we cry, "Abba! Father!" 16 it is the Spirit himself bearing witness with our spirit that we are children of God, 17 and if children, then heirs, heirs of God and fellow heirs with Christ, provided we suffer with him in order that we may also be glorified with him.
Eph 2:21-22 in whom the whole structure is joined together and grows into a holy temple in the Lord; 22 in whom you also are built into it for a dwelling place of God in the Spirit.
James 1:17 Every good endowment and every perfect gift is from above, coming down from the Father of lights with whom there is no variation or shadow due to change.
We do not simply put on Christ's righteousness, God, who holds all things in existence, whose Word formed the universe from nothing, actually removes the reality of our sin so that our sin no longer exists. Thus are we made perfect.
Rom 12:2 Do not be conformed to this world but be transformed by the renewal of your mind, that you may prove what is the will of God, what is good and acceptable and perfect.
Heb 6:4 For it is impossible to restore again to repentence those who have once been enlightened, who have tasted the heavenly gift, and have become partakers of the Holy Spirit...
Eph 3:5-6,19 which was not made known to the sons of men in other generations as it has now been revealed to his holy apostles and prophets by the Spirit; 6 that is, how the Gentiles are fellow heirs, members of the same body, and partakers of the promise in Christ Jesus through the gospel.... and to know the love of Christ which surpasses knowledge, that you may be filled with all the fulness of God.
The promise of Christ is to be filled with all the fullness of God (cf. Col 2:9 on the previous page) - being truly part of the Son, truly participating in the Divine Nature. That is why Paul says what he does in Ephesians 5:1
Eph 5:1 Therefore be imitators of God, as beloved children.
2 Cor 7:1 Since we have these promises, beloved, let us cleanse ourselves from every defilement of body and spirit, and make holiness perfect in the fear of God.
Col 1:28 Him we proclaim, warning every man and teaching every man in all wisdom, that we may present every man mature in Christ.
Rom 16:7 Greet Andronicus and Junias, my kinsmen and my fellow prisoners; they are men of note among the apostles, and they were in Christ before me.
1 Pet 4:6 For this is why the gospel was preached even to the dead, that though judged in the flesh like men, they might live in the spirit like God.
John 14:23 If a man loves me, he will keep my word, and my Father will love him, and we will come to him and make our home with him.
1 Cor 3:16-17,19-20 Do you not know that you are God's temple and that God's Spirit dwells in you? 17 If any one destroys God's temple, God will destroy him. For God's temple is holy, and that temple you are... Do you not know that your body is a temple of the Holy Spirit within you, which you have from God? You are not your own; 20 you were bought with a price. So glorify God in your body.
2 Cor 6:16 For we are the temple of the living God...
Rom 8:9 But you are not in the flesh, you are in the Spirit, if in fact the Spirit of God dwells in you.
2 Cor 13:5 Do you not realize that Christ is in you?
Gal 2:20 I have been crucified with Christ; it is no longer I who live but Christ who lives in me...
Phil 1:21 For to me to live is Christ, and to die is gain.
God is not Father because He made us. He is our Creator, our Master, because He made us. He is Father because He eternally begets the Son. Thus, it is only our portion in the Body of Christ, only when we partake in and participate in the Divine Nature of Jesus Christ, that God truly becomes our Father, and we truly become His sons and daughters. If we want to become children of God, we must be divinized. That is what the sacraments do. They make us truly his children. St. Athanasius stated it most succinctly: "For the Son of God became man so that we might become God." Through the sacramental life, forged in God's covenant with creation and His work on the Cross, we are truly made into the Body of Christ, who is God.
Divinization is the central mission of the Church (Catechism of the Catholic Church, #460, 1988, 1999). All teaching, all ministry, all work is done with the end of bringing all people to the sacraments so that they may be divinized and have a share in the Body of Christ. Our human nature was made in order to be completely immersed in the divine Fire, the consuming, ravishing love of God, in a whirling dance with Him forever, pouring ourselves out perfectly to Him and Him to us, eternal interpenetration with the Eternal. This cannot be accomplished except in Jesus Christ, in His suffering, His cross, His sacraments.