ecclesiology
+ NewThe Trinity in the Great Commission — Matthew 28:19
Matt 28:18-20 commissions the church to baptize "in the name (singular) of the Father and of the Son and of the Holy Spirit." One name, three persons: the baptismal formula is implicitly trinitarian. Augustine's On the Trinity mined this text for the unity of the divine persons, and the Nicene Creed gave the church its trinitarian grammar. Basil and the Cappadocians defended the Spirit's full deity on such baptismal grounds. The baptism commanded here is unfolded theologically in Rom 6:3-4, and the abiding presence of 28:20 echoes the Immanuel of Matt 1:23. The triune name is the church's confession and its commission.
Baptism into Christ — Romans 6 and Matthew 28
Rom 6:3-4 interprets baptism as union with Christ's death and resurrection: "we were buried therefore with him by baptism into death, in order that... we too might walk in newness of life." The sign signifies a real participation. Calvin defined a sacrament as a visible word that seals the promise, and the Catechism treats baptism as the gateway to life in the Spirit. Augustine's debates with the Donatists shaped the church's theology of valid baptism. Baptism is commanded in the Great Commission of Matt 28:19 and grounded in the union of Rom 6:5-11. It is the visible entry into the body addressed in 1Cor 12:13.
The Lord's Supper — 1 Corinthians 11:23-26
1Cor 11:23-26 hands on the words of institution: "this is my body... this cup is the new covenant in my blood... do this in remembrance of me." The meal proclaims the Lord's death "until he comes." Aquinas articulated transubstantiation as the mode of Christ's presence, which Calvin rejected in favor of a true spiritual feeding by the Spirit. The Catechism summarizes the Catholic eucharistic faith. The Supper has been the central sacramental dividing line of the church. The "new covenant in my blood" fulfills Jer 31:31 and the Passover of Exod 12:23. The shared loaf expresses the one body of 1Cor 12:12.
The Church as the Body of Christ — 1 Corinthians 12
1Cor 12:12-27: "for just as the body is one and has many members... so it is with Christ." By one Spirit all are baptized into one body, and the diversity of gifts serves the common good. Augustine's totus Christus — the whole Christ, head and members — expresses this unity, and Calvin treated the church as the mother of believers. The Catechism develops the body-of-Christ image for the communion of saints. The Spirit who distributes gifts here is the same Spirit of John 15:26 and Pentecost in Acts 2:17. The one baptism into one body connects to Rom 6:3 and Eph 4:4-6.
Pentecost and the Outpoured Spirit — Acts 2
Acts 2:16-21 interprets Pentecost as the fulfillment of Joel: "I will pour out my Spirit on all flesh." The ascended Christ sends the Spirit, and the last days begin with the birth of the church. Augustine preached Pentecost as the love of God poured into the church, the reversal of Babel, and Calvin treated the outpouring as the public inauguration of the Spirit's new-covenant ministry. The Spirit given here is the same who proceeds in John 15. Pentecost fulfills the promise of the Spirit in John 15:26 and the new heart of Ezek 36:27. It constitutes the one body of 1Cor 12:13 and looks ahead to the consummation of Rev 21:3.