Ferris Bueller famously quipped, when referring to life, that “If you don’t stop and look around once in a while you could miss it.” By which I have always taken him to mean that the important things in life (e.g. family, friends, a day off, etc.) can all too easily go unnoticed or unappreciated— not because we don’t see them but because we are either moving too fast or see them so often that we fail to recognize their significance.
There is a little phrase in the New Testament like that— a phrase we see so often, especially in the letters of Paul, that we have a tendency to read past it without giving it much thought. And yet Paul's whole theology is essentially contained within these two words. Those words are “in Christ.”
John Stott tells us that, "The expressions ‘in Christ,’ ‘in the Lord,’ and ‘in Him’ occur 164 times in the letters of Paul alone, and are indispensable to an understanding of the New Testament.” This one densely packed, theologically charged and often overlooked phrase turns out to be the hermeneutical key to Paul's thought and the hinge on which the entire canon of Scripture turns.
If it is that important, we should ask ourselves, what does it mean to be “in Christ”? Let's "stop and look around" to see if we can discern its significance.
What does it mean to be “in Christ”?
To be in Christ means to be identified by God with Jesus and not with Adam. More specifically, it means to be under the representative headship of Christ and not under the representative headship of Adam.
Adam was the representative head of the first humanity in two senses. First, he was the representative head of humanity in a genealogical sense. He was the first man. Therefore, all humanity is rightfully said to have descended from him. In other words, he was the source from which the first humanity flowed (i.e. its natural progenitor). Which is why the Bible characterizes descendants as being in the loins of their fathers. For example, it says in Hebrews 7, “One might even say that Levi, who collects the tenth, paid the tenth through Abraham, because when Melchizedek met Abraham, Levi was still in the body of his ancestor.” We were all in the body of Adam in this sense (i.e. part of his family born according to the flesh).
This genealogical sense of headship entails a second sense of headship. Adam was also the representative head of humanity in a political or covenantal sense. He was the man in charge— first not only in ancestral order but in hierarchical authority as well. He was the first man to occupy the divinely elected office of Priest-King. Therefore, he had the legal right and responsibility to speak and act on behalf of his people before God. We see the logic of this type of headship in a text like Exodus 28 where Moses is given instructions for Aaron: “Take two onyx stones and engrave on them the names of the sons of Israel...Aaron is to bear the names on his shoulders as a memorial before the Lord.” As High Priest, Aaron represented the sons of Israel before God. In his role as the head of national worship, Aaron offered sacrifices on behalf of the rest of the nation. That is the logic of representation: the one stands in for and acts on behalf of the many. We were all “in Adam” in this sense as well. We were part of his body politic. We were the legally recognized subjects that Adam represented before God in the Garden.
By way of contrast, Christ is the representative head of a new humanity. First, He is the head of humanity in the genealogical (Heb. 2:11-13) or organic sense (Jn. 15:5). He is the "Second Adam” (1 Cor. 15:45-48). Therefore, all new humanity is rightfully said to have descended from Him. He is the source from which the second humanity flows (i.e. its supernatural progenitor). Which is why the Bible characterizes His people as undergoing a second birth. As Jesus explains in John 3, “Truly, truly, I say to you, unless one is born again he cannot see the kingdom of God...That which is born of the flesh is flesh, and that which is born of the Spirit is spirit.’” We are all in the body of Christ in this sense (i.e. part of his family born according to the Spirit).
Again, this genealogical sense of headship entails a second sense of headship. Christ is also the representative head of humanity in a covenantal sense. He is first not only in ancestral order but in hierarchical authority as well. He is the leader of the new humanity, the first man to occupy the divinely elected office of Priest-King of the new creation. Therefore, He has the legal right and responsibility to speak and act on behalf of His people before God (in matters of Church and State). Echoing the sentiments of Exodus 28, we see the logic of this type of headship in a line from the aptly entitled hymn “Before the Throne of God Above,” which says, "My name is graven on His hands, My name is written on His heart.” As Aaron bore the names of the sons of Israel before God, Jesus, the great High Priest in the order of Melchizedek, bears the names of the elect before God (Heb. 7:15-17). So, we are all “in Christ” in this sense as well. We are part of His body politic. We are the legally recognized subjects Christ represented before God at Calvary.
We see this contrast between Christ's headship and Adam's headship in Romans 5 where Paul writes, “Just as one trespass resulted in condemnation for all people, so also one righteous act resulted in justification and life for all people. For just as through the disobedience of the one man the many were made sinners, so also through the obedience of the one man the many will be made righteous.”
Originally, we inherited our status and condition from Adam. “In Adam,” our first representative head, our shared legal status was “guilty” and our shared human condition was “fallen.” In Adam we were all covenant breakers with corrupt natures. As it says in the 1689 London Baptist Confession when discussing Adam and Eve eating the forbidden fruit: “They being the root, and by God's appointment, standing in the room and stead of all mankind, the guilt of the sin was imputed, and corrupted nature conveyed, to all their posterity descending from them by ordinary generation...” (LBC 6.3).
However, now we inherit a new status and condition from Christ. “In Christ,” our second representative head, our shared legal status is “righteous” and our shared human condition is “upright.” In Christ we are all covenant keepers with holy nature's (Romans 8:29). As we might say then, in discussing Jesus’ obedient death: He being the root of all renewed mankind, the righteousness of this obedience was imputed, and the same life in obedience and pure nature conveyed, to all His posterity descending from Him by extraordinary generation.
This is the double exchange: God exchanges our old covenant status (guilty) and old creation condition (dead) in Adam with our new covenant status (righteous) and new creation condition (alive) in Christ (2 Cor. 5:17). In short, we have exchanged the headship of Adam for the headship of Christ. We have been transferred from the family and kingdom of Adam into the family and kingdom of Jesus (Col. 1:13).
This is critically important to our salvation, as Jesus is the only person legally qualified to fulfill the conditions of the covenant for us. He could not have lived the life we should have lived or died the death we should have died in our place unless He met the criteria of a representative head. He had to be the Second Adam, our representative Kinsman and King, or else we could not have been credited His covenant obedience (justification) or shared in His covenant reward (resurrection life).
Simply put, to be “in Christ” means that Jesus is our representative head. He stands for us. Therefore, what He does can rightfully be credited to us and what happened to Him can rightfully be said to have happened to us. As Paul says, “...count yourselves dead to sin but alive to God in Christ Jesus” (Rom. 6:11). I.e. in virtue of Christ's position as our representative, His death is our death, His resurrection our resurrection. And it is in virtue of our union with Christ, affected by the Spirit through faith, that we take on His name and nature.
In closing, representative headship is the answer to what it means to be in Christ, while regeneration is the answer to how we come to be in Christ. As Michael Horton writes, "Union with Christ is not to be understood as a “moment” in the application of salvation to believers. Rather, it is a way of speaking about the way in which believers share in Christ in eternity (by election), in past history (by redemption), in the present (by effectual calling, justification, and sanctification), and in the future (by glorification). Nevertheless, our subjective inclusion in Christ occurs when the Spirit calls us effectually to Christ and gives us the faith to cling to him for all of his riches.” And of course, if we were to ask why we are in Christ, the answer can only be because of “the love of God in Christ Jesus our Lord” (Rom. 8:39).