The Three Unions

or the relation between God and salvation

God is the Gospel.[1] There is no salvation without God, and no knowing God without salvation. For God has revealed Himself such that we cannot know Him truly without knowing Him as God our Savior (Isaiah 43:3; Titus 1:3, 2:10, 2:13, 3:4). This essay sets out to show the fundamental relation between God and salvation by seeing salvation as three unions, without which life in God would be impossible and empty.

It is, thankfully, impossible to fully articulate the magnitude of the relation between salvation and God.[2] However, perhaps the best ways to communicate the essence of salvation is to speak of it as three unions.[3] These unions are “the eternal union within the Trinity,” the union in the Son “of the human and divine natures of Christ” “in one Person,” and “the union of the saints with God by the Spirit.”[4] We begin with the first of these.

Union within the Trinity

The foundational and defining union at the heart of Christianity and of all the goodness that comes to us in salvation is the Trinity: Father, Son, and Holy Spirit.[5] From eternity, God has enjoyed the happy fellowship of His Triunity. He did not become Father, or Son, or the life-giving Spirit – God is who He is in the relationship of the Trinity.[6] It is so natural to Him that John describes who God is as “light” and “love,” communicating the perfect fellowship that He has in Himself (1 John 1:5, 4:8). Eternal life, as the duration of God’s goodness, is thus described by Jesus Himself as knowing “the One true God, and Jesus Christ” whom the Father sent (John 17:3).[7] This is God’s life, eternal to Him by essence in fellowship. Therefore “He is the true God and eternal life” (1 John 5:20).

Jesus is the only way of knowing and having this life (through the second and third unions), as proven by the Son being the object of our faith for salvation (John 20:31). Jesus is “exactly what the Father is like.” There is no God unlike Jesus hiding behind Him (John 14:9).[8] The relationship Jesus shows between Himself and His Father is the relationship they enjoy in the Spirit as Trinity from eternity.

“Jesus… reveals to us eternity. Not a lonely, quiescent God, as neither mind can conceive nor affection grasp, but a God in whom, from all eternity, there was fulness of life and love and blessedness, the Father loving the Son, and the Spirit knowing the depths of the Godhead.”[9]

When Jonathan Edwards sought to communicate who the Triune God is, he picked up the image of the whirlwind from Ezekiel’s vision (Ezekiel 1:4). “This fire,” wrote Edwards, “infolding itself, does especially represent the Deity before the creation of the world… when all God’s acts were only towards Himself, for then there was no other being but He.”[10] The “flames of divine love are received and infolded into the bosom of the [Triune] Deity.”[11] This enfolding is proper and natural to God alone in His fullness. It is His internal triune glory, and His external glory is the radiation or communication of that same fullness.[12] If God was not enfolding within Himself, He would not have “fullness” in Himself, or “irradiate [His saints] with His glory” in the third union, or send His Son for the second union.[13]

The kind of love that characterizes God as He is would not be feasible if that intra-Trinitarian love was not natural to God. Put differently, it is because God is in essence Trinity from all eternity that God is love. The Father is not Father by “his will and intention” but is Father by nature in relation to the Son.[14] All of God’s attributes He has naturally by virtue of His being Trinity.[15] God’s love is not merely a characteristic of God as though He could discard it,[16] nor is there another bond outside of the loving unity of the Persons,[17] but who God is in His Being is the actual substance of their love in natural unity.[18] This is why Edwards speaks of the Spirit as “the bond of this union” between Father and Son (and the ground for the other two unions).[19] The love of God is not dispensable to God’s essence any more than the Spirit is dispensable to the Trinity, though they may be distinguished in this: while the natural unity is not communicable to us, the natural love is.[20] To explain this, we need to turn to the second union.

Union in Incarnation

For all eternity, the Father has given Himself without measure to the Son by the Spirit (as seen in the baptism of Jesus),[21] and the Son has His identity and joy in this relationship with His Father.[22] The incarnation – “the union of God and man in the person of Jesus. Fully God, fully man, fully one, forever.”[23] – and what flows from that union, is the Son sharing what is His.[24] “…the Father gives all his glory, his love, his blessing, his very self exclusively to his Son—and he then sends his Son to share with us his fullness.”[25] This happens “when God takes… dust into unity of his person.”[26]

God had always made Himself known by His humble condescension in the Son before His incarnation.[27] Yet in the incarnation so many blessings are accomplished in Christ as He is made a perfect Savior for sinners (Hebrews 5:9) that numbering them is like “gazing at the open sea and trying to count the waves.”[28] Tolkien marveled at it when he wrote that “The Birth of Christ is the Eucatastrophe of Man’s history.[29] The Resurrection is the Eucatastrophe of the story of the Incarnation.”[30] Immanuel is the Eucatastrophe in humanity’s otherwise hopeless story.[31] For the incarnation is primarily about the gift of life: it is the inception of a new, living humanity.

Sinners needed a new humanity because sinners need true salvation: sonship. Adam was created in the image of God to be the created son of God (Luke 3:38) – created to truly enjoy the Father and reflect the relationship of the natural Son (Romans 5:14).[32] Ontologically made for relationship with God (something that can never be lost, for to be a human being is to be made in the image of God),[33] in Adam, humanity rejects its created sonship.[34] Adam failed to live the life of a son – he did not respond to the Fathers love in trust and affection. Where Adam died (and humanity in him), the true Son of God lived – “fully alive in the Spirit.”[35] This was so that the new humanity may live in Him (Romans 5:19).[36]

The incarnation was “the downward movement of God to us.”[37] In the incarnation (and by extension, on the cross), Christ takes to Himself a human nature, and bears the catastrophic consequences of the rejection of sonship by Adam: the wrath of God (Isaiah 53). He was made sin that humanity in sin might be reconciled to God in Him (2 Corinthians 5:18-21; 1 Peter 3:18). As truly human, Christ died for sinners – physically and spiritual – so that in His resurrection and ascension sinners would share in His life through the third union.[38] Christ took on flesh to take what naturally belonged to His bride upon Himself, and give what is naturally His to her through adoption and participation. When the Spirit indwells in the third union, He points to Christ in this second union. For the incarnation (including Jesus’ life, death, resurrection and ascension) is not merely the way we are saved.[39] It is in union with Jesus Christ of Nazareth that we see and have eternal life (1 John 1:1-3).[40] Who God is within Himself and how God reveals Himself are perfectly consistent.[41] God does not invent the life He shares with us in salvation.[42] It is how John can write “God is love” (1 John 4:8) and define love as God the Father sending the Son to be our atoning sacrifice (1 John 4:9-10).[43] “The self-humiliation of the Son was the perfect presentation of the nature of the Father”[44]

Jesus is the last Adam (1 Corinthians 15:45): the true Son, naturally and perfectly. Christ unites in Himself, that is, in His Person, two natures that are “very different and essentially distinct from each other” so that humanity may “share and participate in the divine nature.”[45] Humans participate in this through union with “the head of a new, Spirit-filled humanity.”[46] “The oldness that was in Adam” is replaced by “the newness that is in Christ.”[47] All those in Christ Jesus enjoy this life (Galatians 2:20; Colossians 3:1-4), and to this third union we now turn.

Union in Christ

This third union is marriage to Christ, adoption by the Father, and participation in the Spirit. In this union, sinners are no longer without Christ, sonship, or the Spirit. This union is the actualization of salvation, and the possession of God.[48]

Martin Luther described salvation as a marriage of Christ to His church in this way: “By the wedding ring of faith [Christ owns] the sins, death, and pains of hell which are his bride’s” as what is hers is “laid upon Christ and swallowed up by him.”[49] As in marriage to be married is the thing itself, so also in salvation to have faith is to have Christ Himself and all that is in Christ. To enter into Christ is to enter salvation (just as Noah entered the Ark).[50] By Christ’s taking the church as His own (through the Spirit giving life and faith in Him), the church has Christ as her own – all that is naturally His, He shares with her as the one eternal Son. What Christ purchased is her possession.[51] Where Christ is, in His place and status as the righteous Son of God, there she is in Him (Ephesians 2:6). Where He goes in the fullness of her humanity, there she goes in the fullness of His Sonship (Hebrews 6:19-20).

Just as the Son takes the church as His own in marriage, so also the Father takes the church as His own through adoption into Christ. By true union in Christ by adoption, because He has the natural and true union with God, Christians have union with the Triune God. Hence, “it is fit that we, that are sons by adoption, should have communion with the Father in the Son by nature” for “[God] delights in us, because we are one with Christ, in whom he beholds us.”[52] We are made legally the children of God in Christ, and know the love of the Father because we are in Jesus Christ. We are so united to the natural Son that in Him we enjoy the full love of the Father for the Son (“loved them even as you loved me . . . because you loved me before the foundation of the world . . . that the love with which you have loved me may be in them, and I in them.” – John 17:23-26), signaled by the Spirit of God’s love being “poured into our hearts” (Romans 5:5).

The Spirit is the seal of our adoption by the Father in the Son. “God conveys all by the natural Son to the adopted sons” by the Spirit.[53] In this third union, sinners have union with the Trinity (John 14:20, 2 Corinthians 13:14). This is why Edwards described the Spirit as “the summum of all good . . . the fullness of God.”[54] We have the Spirit from the Father by Christ (John 14:26; Romans 8:9), and by having Him we are in Christ as adopted by Christ (John 14:18).

The gift of salvation is the promised Spirit Himself (Galatians 3:14).

“The inheritance that Christ has purchased for the elect, is the Spirit of God . . . in his vital indwelling in the heart, exerting and communicating himself there, in his own proper, holy, or divine nature. . . . and hence the Spirit is often spoken of as the sum of the blessings promised in the gospel.”^[55]

When the incarnate Christ died on the cross, paying His life, He purchased life for sinners (Galatians 3:13). The Spirit, as always given to the Son as the substance of the Father’s love, is given without measure to the same incarnate Jesus of Nazareth, and in His resurrecting life, “the oil that is poured on the head of the Church runs down to the members of His body….”[56] The one Spirit indwells individual believers (who are separated from God’s unity of essence and were separated from Him in hostility) and makes them all one as the body of Christ (Ephesians 4:4-6).[57] By this union believers enjoy the natural life of the Trinity, and partake in God’s natural love and light.[58] Loved in the Son – even as His own mystical body.[59]

Conclusion

The three unions prove that the doctrines of God and salvation are in perfect union. Out of the overflow of Triune love, Jesus became what He was not by nature to bring sinners into participation with who He is by nature. In Christ we have Him, His Father, and His Spirit – the eternal life of the one true God. The Trinity is salvation.

Word count: 2,200

Bibliography

• Calvin, John. Commentary on Philippians, Colossians, and Thessalonians. Grand Rapids, Michigan: Christian Classics Ethereal Library, nd.
• Calvin, John. Commentary on the Gospel According to John, Volume 2. Translated by William Pringle. Grand Rapids, Michigan: Christian Classic Ethereal Library.
• Cyril of Alexandria. A Commentary upon the Gospel According to S. Luke, Part 1. Translated by R. Payne Smith. Oxford: Oxford University Press, nd.
• Cyril of Alexandria. Commentary on John, Volume 2. Ancient Christian Texts. Edited by Joel C. Elowsky. Translated by David R. Maxwell. Downers Grove, Illinois: InterVarsity Press, 2015.
• Edwards, Jonathan. An Unpublished Essay on the Trinity. Monergism, nd.
• Edwards, Jonathan. The Works of Jonathan Edwards, Volume One. Grand Rapids, Michigan: Christian Classics Ethereal Library, nd.
• Edwards, Jonathan. The Works of Jonathan Edwards, Volume Two. Grand Rapids, Michigan: Christian Classics Ethereal Library, nd.
• Edwards, Jonathan. Treatise on Grace. Grand Rapids, Michigan: Christian Classics Ethereal Library, nd.
• Fairbairn, Donald and Ryan M. Reeves. Creeds and Confessions: Tracing the Development of the Christian Faith. Grand Rapids, Michigan: Baker Academic, 2019.
• Fairbairn, Donald. Life in the Trinity: An Introduction to Theology with the Help of the Church Fathers. Downers Grove, Illinois: InterVarsity Press, 2009.
• Ferguson, Sinclair. The Holy Spirit: Contours of Christian Theology. Downers Grove, Illinois: InterVarsity Press, 1996.
• Ferguson, Sinclair. The Whole Christ: Legalism, Antinomianism, and Gospel Assurance—Why the Marrow Controversy Still Matters. Wheaton, Illinois: Crossway, 2016.
• Goodwin, Thomas. The Works of Thomas Goodwin, D.D., Volume 1. London: James Nisbet and Co., nd.
• Goodwin, Thomas. The Works of Thomas Goodwin, D.D. Volume 9: A Discourse Of Election; A Discourse Of Thankfulness. London: James Nisbet and Co., nd.
• Gunton, Colin E. Gunton. Father, Son & Holy Spirit: Toward a Fully Trinitarian Theology. London: T&T Clark, 2003.
• Hames, Daniel. Cyril of Alexandria: His Life and Impact. Early Church Fathers. Geanies House, Fearn, Ross-shire: Christian Focus Publications Ltd, 2024.
• Hames, Daniel. God Shines Forth: How the Nature of God Shapes and Drives the Mission of the Church. Wheaton, Illinois: Crossway, 2022.
• Hastings, W. Ross. Jonathan Edwards and the Life of God: Toward an Evangelical Theology of Participation. Minneapolis: Fortress Press, 2015.
• Luther, Martin. Career of the Reformer: I, Vol. 31 of Luther’s Works, American edition. Edited by Harold J Grimm and Helmut T. Lehmann. Philadelphia: Muhlenberg Press, 1957.
• Mead, Peter. Lost in Wonder: A Biblical Introduction to God’s Great Marriage. Geanies House, Fearn, Ross-shire: Christian Focus Publications Ltd, 2016.
• Mead, Peter. Pleased to Dwell: A Biblical Introduction to the Incarnation. Bell and Bain, Glasgow: Christian Focus, 2014.
• Ortlund, Dane. Gentle and Lowly: The Heart of Christ for Sinners and Sufferers. Wheaton, Illinois: Crossway, 2020.
• Piper, John. God is the Gospel: Meditations on God’s Love as the Gift of Himself. Weaton, Illinois: Crossway Books, 2005.
• Polhill, Edward. Speculum Theologiae in Christo. Monergism, nd.
• Reeves, Michael. Delighting in the Trinity: An Introduction to the Christian Faith. Downers Grove, Illinois: InterVarsity Press, 2012.
• Reeves, Michael. Overflow: How the Joy of the Trinity Inspires Our Mission. Chicago Illinois: Moody Publishers, 2021.
• Reeves, Michael. “Problem of Sin: The Story Gone Wrong.” 2013. https://www.unionpublishing.org/resource/the-story-gone-wrong/
• Reeves, Michael. Rejoicing in Christ. Downers Grove, Illinois: 2015.
• Saphir, Adolph. Christ and the Church: Thoughts on the Apostolic Commission. Paternoster Row: The Religious Tract Society, nd.
• Scrivener, Glenn. 321: The Story of God, the World and You. Leyland, England: 10Publishing, 2014.
• Sibbes, Richard. The Complete Works of Richard Sibbes, D.D. Volume IV. London: James Nisbet and Co., nd.
• Sibbes, Richard. The Complete Works of Richard Sibbes, D.D. Volume VI. Edinburgh: John Craig and Son, nd.
• St. Athanasius. On the Incarnation. Grand Rapids, Michigan: Christian Classics Ethereal Library, nd.
• Strachan, Owen. Reenchanting Humanity: A Theology of Mankind. Geanies House, Fearn, Ross-shire: Christian Focus Publications Ltd, 2019.
• Torrance, Thomas F. Torrence. The Christian Doctrine of God: On Being Three Persons. London: Bloomsbury T&T Clark, 2016.
• Tolkien, J.R.R. The Monsters and the Critics and Other Essays. Edited by Christopher Tolkien. Boston: Houghton Mifflin Company, 1984.
• White, James R. The Forgotten Trinity: Recovering the Heart of Christian Belief. Minneapolis, Minnesota: Bethany House, 1998.

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[1] John Piper, God is the Gospel: Meditations on God’s Love as the Gift of Himself (Weaton, Illinois: Crossway Books, 2005). Cf. Sinclair Ferguson, The Whole Christ: Legalism, Antinomianism, and Gospel Assurance—Why the Marrow Controversy Still Matters (Wheaton, Illinois: Crossway, 2016), 37-56.

[2] Michael Reeves, Rejoicing in Christ (Downers Grove, Illinois: 2015), 21.

[3] Peter Mead, Glenn Scrivener, W. Ross Hastings, and Adoph Saphir use the three unions explicitly. Others do not use the phrase, but their theology could very easily be described as centered around these three unions. Among these are Jonathan Edwards, John Calvin, Richard Sibbes, Edward Polhill, Michael Reeves, Cyril of Alexandria, and others. See: Peter Mead, Lost in Wonder: A Biblical Introduction to God’s Great Marriage (Geanies House, Fearn, Ross-shire: Christian Focus Publications Ltd, 2016), 18-19. Glenn Scrivener, 321: The Story of God, the World and You (Leyland, England: 10Publishing, 2014). W. Ross Hastings, Jonathan Edwards and the Life of God: Toward an Evangelical Theology of Participation (Minneapolis: Fortress Press, 2015), 2. Adolph Saphir, Christ and the Church: Thoughts on the Apostolic Commission (Paternoster Row: The Religious Tract Society, nd.), 87-88. Edward Polhill, Speculum Theologiae in Christo (Monergism, nd.), 82. Jonathan Edwards, Treatise on Grace (Grand Rapids, Michigan: Christian Classics Ethereal Library, nd.), 29. John Calvin, Commentary on the Gospel According to John, Volume 2, trans. William Pringle (Grand Rapids, Michigan: Christian Classic Ethereal Library), 111-112.

[4] Hastings, Jonathan Edwards and the Life of God, 2. Saphir, Christ and the Church, 87

[5] Michael Reeves, Delighting in the Trinity: An Introduction to the Christian Faith (Downers Grove, Illinois: InterVarsity Press, 2012), 18, 129-130. See also James R. White, The Forgotten Trinity: Recovering the Heart of Christian Belief (Minneapolis, Minnesota: Bethany House, 1998), 10

[6] Reeves, Delighting in the Trinity, 34.

[7] Jonathan Edwards, The Works of Jonathan Edwards, Volume One (Grand Rapids, Michigan: Christian Classics Ethereal Library, nd.), 854. See also Donald Fairbairn, Life in the Trinity: An Introduction to Theology with the Help of the Church Fathers (Downers Grove, Illinois: InterVarsity Press, 2009), 29.

[8] Michael Reeves, Overflow: How the Joy of the Trinity Inspires Our Mission (Chicago Illinois: Moody Publishers, 2021), 46.

[9] Saphir, Christ and the Church, 80-81

[10] Jonathan Edwards, The Works of Jonathan Edwards, Volume Two (Grand Rapids, Michigan: Christian Classics Ethereal Library, nd.), 2121-2122.

[11] Edwards, The Works of Jonathan Edwards, Volume Two, 2121.

[12] Edwards, The Works of Jonathan Edwards, Volume One, 854.

[13] John Calvin, Commentary on Philippians, Colossians, and Thessalonians (Grand Rapids, Michigan: Christian Classics Ethereal Library, nd.), 289. See also Daniel Hames, God Shines Forth: How the Nature of God Shapes and Drives the Mission of the Church (Wheaton, Illinois: Crossway, 2022), 72.

[14] Cyril of Alexandria, Commentary on John, Volume 2, Ancient Christian Texts, ed. Joel C. Elowsky, trans. David R. Maxwell (Downers Grove, Illinois: InterVarsity Press, 2015), 422.

[15] Hames, God Shines Forth, 58-59.

[16] Daniel Hames, Cyril of Alexandria: His Life and Impact, Early Church Fathers (Geanies House, Fearn, Ross-shire: Christian Focus Publications Ltd, 2024), 107.

[17] Thomas F. Torrence, The Christian Doctrine of God: On Being Three Persons (London: Bloomsbury T&T Clark, 2016), 124.

[18] For a fuller discussion of this, see Colin E. Gunton, Father, Son & Holy Spirit: Toward a Fully Trinitarian Theology (London: T&T Clark, 2003), 43-50. Cf. Torrance, The Christian Doctrine of God, 112-202.

[19] Edwards, Treatise on Grace, 29

[20] Fairbairn, Life in the Trinity, 36. For more on the alienation of Christ on the cross in light of this truth, see Fairbairn, Life in the Trinity, 174-179.

[21] Reeves, Delighting in the Trinity, 29-30

[22] Reeves, Rejoicing in Christ, 89.

[23] Peter Mead, Lost in Wonder, 203.

[24] Reeves, Delighting in the Trinity, 63

[25] Reeves, Delighting in the Trinity, 71

[26] Richard Sibbes, The Complete Works of Richard Sibbes, D.D. Volume VI (Edinburgh: John Craig and Son, nd.), 461.

[27] Peter Mead, Pleased to Dwell: A Biblical Introduction to the Incarnation (Bell and Bain, Glasgow: Christian Focus, 2014), 203. See also Dane Ortlund, Gentle and Lowly: The Heart of Christ for Sinners and Sufferers (Wheaton, Illinois: Crossway, 2020), 147.

[28] St. Athanasius, On the Incarnation (Grand Rapids, Michigan: Christian Classics Ethereal Library, nd.), 43. Cf. Ortlund, Gentle and Lowly, 177.

[29] By Eucatastrophe, Tolkien meant something like the turning point of a story that secures, beyond all doubt, good. For more on this, see J.R.R. Tolkien, The Monsters and the Critics and Other Essays, ed. Christopher Tolkien (Boston: Houghton Mifflin Company, 1984), 153-157

[30] Tolkien, The Monsters and the Critics, 156.

[31] Hames, Cyril of Alexandira, 135.

[32] Michael Reeves, “Problem of Sin: The Story Gone Wrong,” 2013, https://www.unionpublishing.org/resource/the-story-gone-wrong/ 15:00-16:20.

[33] Owen Strachan, Reenchanting Humanity: A Theology of Mankind (Geanies House, Fearn, Ross-shire: Christian Focus Publications Ltd, 2019), 29-31.

[34] Hames, God Shines Forth, 74-76

[35] Reeves, Rejoicing in Christ, 56.

[36] Fairbairn, Life in the Trinity, 154.

[37] Donald Fairbairn and Ryan M. Reeves, Creeds and Confessions: Tracing the Development of the Christian Faith (Grand Rapids, Michigan: Baker Academic, 2019), 55, 97.

[38] Fairbairn, Life in the Trinity, 175.

[39] Hames, Cyril of Alexandria, 73.

[40] Sibbes, The Complete Works of Richard Sibbes, Volume VI, 404.

[41] Torrance, The Christian Doctrine of God, 113-114. Cf. Sibbes, The Complete Works of Richard Sibbes, D.D. Volume VI, 456.

[42] Hames, Cyril of Alexandria, 120.

[43] Fairbairn, Life in the Trinity, 159-160.

[44] Mead, Pleased to Dwell, 177.

[45] Cyril, Commentary on John, Volume 2, 734.

[46] Reeves, Rejoicing in Christ, 56.

[47] Cyril of Alexandria, A Commentary upon the Gospel According to S. Luke, Part 1, trans. R. Payne Smith (Oxford: Oxford University Press, nd.), 48.

[48] Hames, Cyril of Alexandria, 135.

[49] Martin Luther, Career of the Reformer: I, Vol. 31 of Luther’s Works, American edition, ed. Harold J Grimm and Helmut T. Lehmann (Philadelphia: Muhlenberg Press, 1957), 351-352.

[50] Thomas Goodwin, The Works of Thomas Goodwin, D.D. Volume 9: A Discourse Of Election; A Discourse Of Thankfulness (London: James Nisbet and Co., nd.) 72.

[51] Thomas Goodwin, The Works of Thomas Goodwin, D.D., Volume 1 (London: James Nisbet and Co., nd.), 430.

[52] Richard Sibbes, The Complete Works of Richard Sibbes, D.D. Volume IV (London: James Nisbet and Co., nd.), 33.

[53] Sibbes, The Complete Works of Richard Sibbes, Volume IV, 119.

[54] Edwards, Treatise on Grace, 30. See also Polhill, Speculum Theologiae in Christo, 255.

[55] Edwards, The Works of Jonathan Edwards, Volume One, 1304.

[56] Jonathan Edwards, An Unpublished Essay on the Trinity (Monergism, nd.), 7.

[57] Cyril, Commentary on John, Volume 2, 736-737. See also Sinclair Ferguson, The Holy Spirit: Contours of Christian Theology (Downers Grove, Illinois: InterVarsity Press, 1996), 175-176.

[58] Cyril, Commentary on John, Volume 2, 734-735.

[59] Sibbes, The Complete Works of Richard Sibbes, Volume VI, 578.

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