When the Reformers of the sixteenth century turned to the fourth Gospel, they found a multitude of theological treasures: a clear affirmation of the full divinity of Christ; insights into the relationships among the Father, Son, and Holy Spirit; and guidance for the church in their time. For example, John Calvin claimed, “This Gospel is a key to open the door for understanding the rest; for whoever shall understand the power of Christ, as it is here strikingly portrayed, will afterwards read with advantage what the others relate about the Redeemer who was manifested.”
Reformation commentators ruminated on the meaning and implications of such claims for shedding light on doctrines like the Trinity, the divinity of Christ, and his incarnation, but also for grasping the saving benefits of Christ’s work in justification (for those “who believed in his name”) and new birth (those born of God as his children, 1:12-13).