On Saturday, I was reading in the Catechism about how Jesus, when united with the Church, forms the “whole Christ” or “total Christ” (Christus totus). The phrase comes from the writings of St. Augustine. Here’s what the Catechism says on it:
795 Christ and his Church thus together make up the “whole Christ” (Christus totus). The Church is one with Christ. The saints are acutely aware of this unity:Let us rejoice then and give thanks that we have become not only Christians, but Christ himself. Do you understand and grasp, brethren, God’s grace toward us? Marvel and rejoice: we have become Christ. For if he is the head, we are the members; he and we together are the whole man. . . . The fullness of Christ then is the head and the members. But what does “head and members” mean? Christ and the Church. (St. Augustine, In Jo. ev. 21,8:PL 35,1568.)
Our redeemer has shown himself to be one person with the holy Church whom he has taken to himself. (Pope St. Gregory the Great, Moralia in Job, præf.,14:PL 75,525A.)
Head and members form as it were one and the same mystical person. (St. Thomas Aquinas, STh III,48,2.)
A reply of St. Joan of Arc to her judges sums up the faith of the holy doctors and the good sense of the believer: “About Jesus Christ and the Church, I simply know they’re just one thing, and we shouldn’t complicate the matter.” (Acts of the Trial of Joan of Arc)
I keep asking that the God of our Lord Jesus Christ, the glorious Father, may give you the Spirit of wisdom and revelation, so that you may know Him better. I pray that the eyes of your heart may be enlightened in order that you may know the hope to which He has called you, the riches of His glorious inheritance in His holy people, and His incomparably great power for us who believe. That power is the same as the mighty strength He exerted when He raised Christ from the dead and seated Him at His right hand in the heavenly realms, far above all rule and authority, power and dominion, and every name that is invoked, not only in the present age but also in the one to come. And God placed all things under His feet and appointed Him to be Head over everything for the Church, which is His Body, the fullness of Him who fills everything in every way.
That’s exactly what the Catechism and St. Augustine were saying. The fullness of Christ is found in Christ united with His Body, the Church. You can’t possibly possess one without the other.