Solus Christus

Stephen Wellum and Matthew Barrett discuss why everything centers on the person and work of Jesus Christ

You have spent much of your life studying the person and work of Christ. There are, of course, many doctrines of the faith you could have devoted yourself to, so what drew you to Christology?

You are exactly right that I have spent the last fifteen years thinking about Christology with the goal of publication, and, I must say, it has been a sheer delight and joy. In God’s providence, my former professor and doctoral advisor, John Feinberg, invited me to write God the Son Incarnate: The Doctrine of Christ for the “Foundations in Evangelical Theology” series published by Crossway. Until he invited me, I was working more in the area of theology proper, theological hermeneutics, and theological method, but with his invitation, my attention turned to Christology. As I look back on that moment in my life, I am so thankful that John asked me to write for the series, which sent me in another direction in my research, writing, and teaching. And once I got deeper into the research for the book, I knew that this was the topic to study, and that is certainly an understatement.

In my work on Christology, it dawned on me that everything in systematic theology centers on Christ. To do a Christology one has to grasp how the whole Bible is put together since, if we follow Scripture’s own teaching, our Lord is the center of Scripture and God’s entire plan. Before my publication on Christology I first published with Peter Gentry, Kingdom through Covenant: A Biblical-Theological Understanding of the Covenants, but that book was really the outworking of my study of how the whole Bible is centered in Christ, and how all of the biblical covenants unfold God’s glorious plan of redemption which reaches its fulfillment, terminus, and telos in Christ.

Also, in working on Christology, it has helped me to think more about the doctrine of the Trinity and how the Father, Son, and Spirit have related to each other from eternity (ad intra) and in the economy (ad extra), and then tie the entire discussion to the glorious gospel of God’s sovereign grace.

Studying in the area of Christology has also allowed me to think through methodological and hermeneutical issues on how to draw conclusions from Scripture that are first true to the Bible’s own teaching, and then secondly, to think through what the church has said as we seek to stand on their shoulders and speak the truth today. I cannot thank the Lord enough, and those who made it possible, for allowing me to spend time thinking through, meditating, wrestling with, and growing in my knowledge of our Redeemer, Jesus Christ our Lord. In the end, studying the Jesus of the Bible—his glory, beauty, and majesty—is what draws you to him, which is certainly evidence of God’s work of grace in my life.

Your new book in The 5 Solas Series, Christ Alone: The Uniqueness of Jesus as Savior (Zondervan), just to released. Tell us, what is solus Christus, and why was this particular sola so important to a reformer like Martin Luther?

When one thinks of the differences between the Reformers, like Martin Luther and the Roman Catholic Church, and relates those differences to Christ, one has to reflect carefully on what Luther and the Reformers were professing with solus Christus. What this sola meant was not so much focused on Christ’s unique and exclusive identity as God the Son incarnate. The Roman church, unlike later heretics such as the Socinians, were fully orthodox in their understanding of Christ’s person or identity. They, along with the Reformers, were pro-Nicene and pro-Chalcedonian in their theology proper and Christology. So, when Luther and the Reformers affirmed solus Christus – “in and through Christ alone”—what were they confessing? It is best to say that they were confessing the sufficiency of Christ’s work, something that was lost, or at least undermined in Roman Catholic theology.

Where Rome compromised Christ’s sufficiency was in a couple of areas. First, in the application of Christ’s work, they affirmed Christ paid for our eternal sins, which was applied to us by the church in our baptism where we are infused with Christ’s righteousness. However, as we live our lives and continue to sin, there is the ongoing application of Christ’s work via the sacramental system (specifically penance and the Mass) as we grow in our justification by growing in righteousness and cooperating with God’s grace. In this way, Christ’s obedient life and death for us, as our new covenant head and mediator, is undermined. Christ is not the sole ground of our justification before God, and thus, we are not justified by faith alone in and through Christ alone (solus Christus). For Luther and the Reformers, the sacraments are important but they do not function as they do in Rome’s theology. For Luther, and the Reformers, it is Christ alone in his life and death on the cross, which fully pays for our sin and it is Christ alone who is the sole ground of our justification. Because of who Jesus is and what he has done as God the Son incarnate, there is nothing more that we can add to his work; it is enough now and forevermore. By raising the empty hands of faith, we are declared just before God because our sins are paid in full and his perfect righteousness is ours in covenant union with him.

Second, for Rome there was an inadequate grasp of Christ’s work and our union with Christ by grace through faith. The Reformers taught a proper understanding of Christ’s obedience for us as our Savior. This is especially important in Calvin who thinks deeply about Christ’s obedience for us as the Last Adam. Due to the incarnation, the divine Son becomes human and is thus able to identify with us and be our Savior. In that identification as our covenant representative and substitute, he redeems us. Christ’s entire life, death, and resurrection as our Mediator is for us. In this way, there is nothing we can add to his work; what he has done as the perfect divine Son is enough to pay for our sin, satisfy God’s own righteous requirements, and defeat our enemies. In faith union with Christ, we are clothed in his righteousness, and his work is imputed to us as thus ours, not in terms of legal fiction but actually ours because of our union with our covenant head. In addition, the work of the Spirit is to unite us to our Mediator and to make us alive in him, so that we really have resurrection life and the full legal standing of Christ.

Rome did not teach all of these crucial points tied to Christ’s glorious work, and as a result, Luther and the Reformers, as they argued from Scripture, cried solus Christus! In fact, given our human sin before the holy, righteous triune God, it is only the triune God who can save us by grace alone through faith alone in Christ alone. Our problem before God is so great, and our sin demands God’s eternal judgment, that it is only God himself in sovereign grace who can save us, and this is precisely what he has done in triune agency—by the initiative of the Father, through the Son, and the application work of the Spirit.

Is solus Christus still relevant today? Are there ways, in your estimation, that solus Christus has been abandoned or challenged today?

Solus Christus is as relevant today as the gospel is relevant and true—which it is! Let us think about this in a few areas. First, if we take Scripture seriously in all that it teaches, we have to confess that before God, we are lost and dead in our transgressions and sins. In ourselves, we can do nothing to save ourselves; the triune God must save and he must do it alone. To lose the emphasis on solus Christus ultimately undermines this central point of the entire story and message of Scripture. Solus Christus, then, is as relevant as the gospel is true and relevant!

Second, to affirm solus Christus today is also a stark reminder of some of the challenges we face in doing so. Under the first point I said that if we embrace all that Scripture teaches then solus Christus is precious to us. However, this is part of our challenge. Since the Enlightenment era there has been a consistent assault on biblical, historic Christianity. In our time, this has led many to view Christ simply as one religious figure among many with pluralism functioning as the given of our day. In such a context, solus Christus really does not mean much to people who embrace the “spirit of the age.” Today, in fact, solus Christus is viewed as oppressive and bigoted. This is probably our greatest challenge, something the Reformers did not face in exactly the same way: articulating, defending, and proclaiming first the exclusive identity of Christ and then secondly Christ’s all-sufficient work. Yet, solus Christus can and must be defended for the sake of the truth and God’s glory, and we must do so with sound theology, conviction, and joy.

Third, as we think of the relevance of solus Christus within evangelical theology, sadly, there are some challenges we face from within our camp. Today, there is a lot of discussion surrounding the nature of the cross and a move away from viewing the heart of the cross as penal substitution. In my view, if one moves in this direction, solus Christus, as taught in Scripture and by the Reformers, will be undermined. In addition, within evangelical theology, for example, there is an attempt to redefine the nature of sin, reject a historic Fall, and argue that God’s justice is not retributive—discussions which will undercut the Bible’s view of Christ and his work. Mark it well: solus Christus is a glorious and beautiful truth central to the entire Bible, but it can only be maintained within a Reformation theology of God, humans, sin, and an orthodox Christology. Our challenge within certain segments of evangelical theology is to articulate and defend Reformation theology once again on these very points for what it is: theology which is true to God’s authoritative Word.

In your new book God the Son Incarnate: The Doctrine of Christ you interact with Martin Luther’s communicatio idiomatum (i.e., the communication of attributes). What did Luther believe and how it differed from another reformer like John Calvin?

In the Reformation, there were serious in-house debates on Christology, especially on the issue of the communicatio, and especially between Luther and Calvin. Both of them affirmed they were Chalcedonian in their Christology and for the benefit of doubt, we can agree with this affirmation. Yet, the difference was in the details and the details in Christology are always important!

In the discussion of the communicatio idiomatum, i.e., “the communication or transfer of attributes,” much of the discussion centered on the relationship between Christ’s two natures as united in the one person of the Son. The Chalcedonian Definition (AD 451) taught that in the incarnation, the two natures of Christ were not blended, confused, or changed in terms of their attributes. In Christ, the Creator-creature distinction is maintained in regard to his two natures. All that the Son is in his deity he retains, and the same is said for his human nature. However, Chalcedon also argued that Christ’s two natures were not separated because they were united in the Son, who is the person/subject of both natures.

This Chalcedonian formulation entailed that the Son, as a result of the incarnation, was now able to act in and through both natures. The communicatio, then, was stated like this:

What is true of each nature is true of the Son, but each nature retains its own integrity so that the divine nature remains what it has always been and the human nature remains fully human and it does not take on divine attributes.

With this understanding the church was able to say without contradiction two things simultaneously about Christ: the Son is eternal (as to his divine nature) and the Son is finite (as to his human nature), or that the Son is omnipotent (as to his divine nature) and the Son is weak (as to his human nature). So far so good.

However, Luther wanted to go further, especially as he wrestled with Christ’s presence in the Lord’s Supper. By appealing to the union of natures in the person of the Son, he argued Christ’s divine nature could “communicate” to the human nature the attribute of omnipresence. This is how Luther argued for consubstantiation in the Lord’s Supper. The elements are not transformed into the body and blood of Christ (that was the transubstantiation view of Rome), but Christ is actually present “in, with, and under” the elements. To make sense of this, one has to argue that through the union of natures in the person, the divine nature can “communicate” omnipresence to Christ’s human nature. This was a modification of the historic view of communicatio because it entailed that there was some kind of transfer of attributes between the natures.

Calvin (and Zwingli) reacted strongly to this view. Calvin charged the Lutheran view with flirting with the old heresy of monophysitism, which blended the two natures into just one nature during the incarnation. Luther denied this charge; instead he appealed to the union of natures in the person of the Son as the warrant for his view. Calvin, appealing to Chalcedon and Scripture, argued that Christ’s two natures are not blended and that each nature retains its integrity. Thus, the divine nature remains fully divine, and the human nature remains fully human, which entails that the human nature does not take on the attribute of omnipresence.

Overall, in my view, based on Scripture and Chalcedon, Calvin was correct. To do justice to all that Scripture says, we must distinguish the two natures in Christ and not blend them. No doubt, we must also affirm that the Son is the subject of both natures and is able to act through both natures, but the integrity of Christ’s divine nature and human nature remain. As important as Luther is in many areas, his Christology is defective at this point, and is not the path to follow if one wants to maintain a faithful, biblical, and Chalcedonian Christology.

Some readers may have heard of the “extra”—sometimes called Calvin’s extra, or the extra Calvinisticum. Of course, the phrase can be a misleading nomenclature since many of the Fathers also taught the “extra.” What is the “extra” and how does it help us articulate an orthodox understanding of the hypostatic union?  

Calvin is associated with the extra, but you are correct that what Calvin affirms is consistent throughout the history of the church, and he was not the first to teach it. Interestingly, the association of the extra with Calvin was really from the Lutheran side, and they used it more pejoratively than positively. The reason for this was due to the previous question of the differences between Luther and Calvin on the communicatio and whether Christ’s divine nature communicates its attributes to the human nature.

For Calvin (and the history of the church), the extra affirms that the Son, who is the subject of both natures, is able to act in both natures, and that he, as the Son, is not limited to acting only through his human nature. Extra means “outside.” In the incarnation, the Son added to himself a second nature, namely a human nature. The Son who has always shared the divine nature with the Father and Spirit has always acted as the Son in relation to the Father and Spirit through the divine nature.

However, in the incarnation, the Son is now able to act in his human nature, yet he is also able to act “outside” (extra) of his human nature. How and when he does so is not easy to grasp, yet we must affirm that he can. Texts such as Colossians 1:17 are important in this regard. Even as the incarnate Son, Paul says that the Son continues to uphold the universe, an act not done in a human nature, but an act of the Son in and through his divine nature.

How does the extra help us articulate an orthodox understanding of the hypostatic union? Here are a number of points. First, it is crucial to remember that it is only the person of the Son who is the acting subject of the incarnation. In Christology, persons are acting subjects, not natures.

Second, the person of the Son is able to act through both natures, so the Son is able to live a fully divine life as he has always done, and now able to live a fully human life.

Third, when the Son acts in and through his human nature he does not transgress the limits of that nature; he does not deify his humanity. This is important because this is how the divine Son lives a fully human life, obeys for us in his humanity, and ultimately achieves our redemption in his humanity.

Fourth, the Son is not limited or completely circumscribed by his human nature, he is also able to act “outside” (extra) of it. This avoids any kenotic understanding that in the incarnation the Son set aside his divine attributes, even temporarily. No, in the incarnation, the Son remains what he has always been, the divine Son who is homoousios, or God-equal with the Father and Spirit, yet he is also the man Christ Jesus.

Why is the extra important? As Calvin rightly noted, the extra preserves the full depth and breadth of Scripture regarding Jesus’ full deity and humanity, and it also allows the Son to be truly human and to act in his humanity for us as our Redeemer, while never compromising his deity. Jesus is nothing less than God the Son incarnate.

Stephen J. Wellum is Professor of Christian Theology at The Southern Baptist Theological Seminary. He is also the editor of The Southern Baptist Journal of Theology.