One of the complaints of FV critics is that ‘Union with Christ’ puts the cart before the horse. If we posit Union with Christ as the center and justification, sanctification, etc. flow from that central covenantal/mystical union then, they say, God is having fellowship with sinners. How can a just God join himself to sin? How can a righteous and holy God have a relationship with the unclean, the unrighteous? These critics march their Ordo Salutis out and point triumphantly to the doctrine of justification and say looky here, mister FV Guy, quit messing with the truth. You’ve gotta be justified first then you can be joined to Christ. This is where sanctification comes. And of course, this “then” is only logically speaking and not (I hope)an actual stopwatch sort of formulation. This sounds all high and pious and holy: who could deny that?
Yet there is a problem. How is one justified? By faith alone, of course. And where did that faith come from. It’s a gift of God, so that no one can boast. Right. So God, in his infinite kindness effectually calls sinners, enlivens them, regenerates them, and gives them this brand new present called faith which enables them to call on the Lord Jesus for mercy, salvation, and grace. In other words, in order for anyone to be saved they must be drawn to the Father, by the Spirit, through the Son. Whenever anyone is justified they have always already been brought into the fellowship of the Trinity. Otherwise, we end up with something other than the historic, Reformed doctrine of justification. Where did that faith come from? The fact that joe-filthy-sinner suddenly looks down and sees his filthy rags exchanged for the righteousness of Christ is always due to having been brought into the family of God, the fellowship of the Trinity, through being united to Christ.
Does this mean that the good, holy, and righteousous God has fellowship with sinners? Absolutely. Does this mean that sinners are united to Christ by grace? Absolutely. Does this mean that there is a moment when God has fellowship with sinners apart from Christ? Absolutely not. This is not a description of a temporal chemical reaction. This is the description of how God does what he does. It’s all of grace, it’s all of kindness, and undeserved mercy. This means that union with Christ is the center of that kindness, and justification, sanctification, and all the benefits of Christ flow from that central act of grace and only because of the righteous life, death, resurrection, and ascension of the Righteous One.
One last illustration of this is found in the historic symbols of the Church. We do not say “I believe that there is one God…” We always confess the faith saying, “I believe in one God…,” “I believe in one Lord Jesus Christ,” “I believe in the Holy Spirit…” And this linguistic point is more clear in the original language and somewhat obscured by the ubiquity of the use of the word “in” in modern parlance. But the point is that with the historic church, we perform the action of believing and utilize the instrument of faith from within God, from within the One Creator God, the One Lord Jesus Christ, and the Holy Spirit. Faith is the result of being raised from the death of sin, and there is only one life outside of that death. There is only one way to be alive in this universe. There is only one Life to be joined to. To be made alive means to be joined to the life breath of the Trinity.
It would not have done for Adam to have claimed that he was righteous before the Spirit of God was breathed into his nostrils. Neither of course would it makes sense to say that he became righteous at some point after he was alive either. The point is that when people are made alive, they live. When Adam became a living being, he was a righteous living being. Likewise, when we are re-created, reborn, re-generated to new life in Christ, we live through the power of the Spirit, we believe with the strength of the Spirit, we have faith and are justified through the life-giving power the Spirit, through the work of Christ, all to the praise and glory of God the Father.