Before the end of Christ’s earthly ministry, He promised He would send “the Spirit of truth, who proceeds from the Father” (John 15:26). The Spirit remains with us as the guarantee of the Kingdom to come, working the power of God among us. The Church is the work of the Spirit as much as it is the work of the Son.
The giving of the Spirit to the Church by Christ is also important because it reveals another “aspect” of God to Christians: that God is Triune, He is Father, Son, and Holy Spirit. God is One, but at the same time Three. This mystery is called the Holy Trinity, and over the years the holy saints of the Church have had time and again to defend the doctrine from sliding into error. Some people have claimed that the Persons of the Trinity are just different modes of God, in the same way a person might be a teacher, a wife, and a mother, but this is a heresy called modalism. Others have insisted that only God the Father is truly God and God the Son and God the Holy Spirit are “less” God than the Father, which subordinates two of the Persons of the Trinity and is also a heresy. Trinitarian theology can be complex, but for our day to day lives what we must remember is that all three Persons are equally and totally God, but that we also don’t worship three Gods. It is a great mystery in the Church, but one which was revealed to us by God Himself.
Through Jesus Christ, the Church is able to be in communion with the Trinity, and this is what the Church ultimately is: the assembly (ekklesia in Greek) of God’s people. The Church is the Body of Christ, a part of His physical presence in the world (Ephesians 4:1, 1 Corinthians 12:12,27). The Church is called to be a witness to God’s love for all humanity. We are “the living stones which make up God’s temple.”
Today, we can often be jaded by institutions such as churches. We have culturally become a cynical people, and part of this cynicism is that we have lost sight of the awesome mystery that is the Church--the very people of God, participating in His infinite Life. Sometimes we will see “religion” compared to any other fallible, human institution, corrupt and ineffective. Especially in these times of lightning-fast information, our exposure to large institutions can seem like a jump from one scandal to another and we are faced with just how much humanity can miss the mark. But in those times we must remember that the Church is not just a human body, but a Divine one, and we trust in the promises of God.