Analogy of faith

Today a biblical scholar might balk at bringing 1 John to bear on the Genesis narrative for fear of doing violence to the voice of Genesis, at least not without qualification, but Wesley assumes a natural connection. Reference to Matthew while considering a point in Genesis creates no problems for Wesley precisely because they are all part of the same gospel. To be even more specific, the analogy of faith dictates that all of these verses can be brought to bear on the image of God in humanity because all—Genesis, Matthew, 1 John and so on—together witness to the truth of justification by faith. Why? Because God has authored both the Scripture that teaches justification as well as the lives whose need for salvation Scripture reveals by its teaching on justification.— Reading the Way to Heaven, page 64