The WESTMINSTER LARGER Catechism

WLC 69. What is the communion in grace which the members of
the invisible church have with Christ?

A. The communion in grace which the members of the invisible church have with Christ,
is their partaking of the virtue of His mediation, in their justification,1 adoption,2 sanctification, and whatever else, in this life, manifests their union with Him.3

Proofs

1Rom 8:30; 2Eph 1:5; 31Cor 1:30

We saw, earlier that "the members of the invisible church by Christ enjoy union and communion with him in grace and glory" (WLC 65); then in the last question what is meant by union with Christ. Union with Christ has to do with our being one with Christ. We are brought into spiritual and mystical union with Christ through the work of the Holy Spirit in our effectual calling.

This union with Christ paves the way for the members of the invisible church to enjoy communion or fellowship with Christ, which communion also manifests our union with Christ.

We may roughly illustrate this thought by thinking of a marriage between a husband and his wife. The marriage is the union, but the communion,—which also confirms that they are truly married,—is their undying faithfulness and love to each other, the issue of children, their growing to be more and more like each other, the home they built together, etc. The illustration of course breaks down when we consider the fact that in our communion with Christ, He ultimately receives nothing from us that is of benefit to Him, whereas in Christ, we "blessed… with all spiritual blessings" (Eph 1:3). This is why our answer speaks of our ‘partaking’ of what Christ procured through His mediation for us, rather than our ‘sharing’ with Him our life. Our communion with Christ is in a sense one-sided.

Our communion with Christ will be explained in details from WLC 70-81, but here is an introductory summary.

We shall leave the detailed discussions for later, but it is instructive for us to consider the phrase "virtue of His mediation" in this summary.

Firstly, consider the word ‘mediation.’ This word indicates to us we really deserve God’s wrath, and that apart from Christ we are alienated from Him. As our Mediator, Christ reconciled to God and secured for us the spiritual blessings that constitute our communion with Him.

But secondly, consider the word ‘virtue’. What does ‘virtue’ mean? Our Shorter Catechism in the parallel question asks: "What benefits do they that are effectually called partake of in this life?" (WSC 32). The word ‘virtue’ then would include the idea of benefits, or good things that Christ has procured for us. But ‘virtue’ says a bit more than ‘benefit’, for it indicates that the mediation of Christ is efficacious and powerful, and therefore will accomplish what it was intended to accomplish. This mediatorial work is completed historically, but the application of the benefits purchased through it is still not completed. The outpouring of the benefits of Christ’s mediation is continuing today and will continue forever. W