Paul's own experience of God's saving activity through Christ the messiah and risen Lord and through the Holy Spirit meant for him, as it did for the Early Church before him, an expanded understanding of the one God as Father and Son (the Lord Jesus Christ) and Holy Spirit. This study attempts to offer a contribution to the deeper understanding of this fact which Paul expressed through the trinitarian formulae in his letters. These formulae are analyzed from various perspectives, namely, their syntactical characteristics, meaning, function, and 'trinitarian' implications, These implications paved the way for a dynamic redefinition of God in the 'trinitarian' direction. The dense theological formulations are significant for the right understanding of Paul's Gospel, Paul's apostleship, ministry, and the Christian life with its final fulfillment.