Since the earliest days of the church, scriptural interpreters have noticed similarities between the writings of Paul and John. These similarities have become a topic of intense debate among biblical scholars.

In Paul and John in Harmony, world-renowned New Testament scholar Michael Gorman looks in depth at significant parallels between the Gospel of John and 1 John and the Pauline letters. Gorman explores texts such as Philippians 2, John 13, and John 15 and themes such as participating in Christ and the Father's double sending of the Son and the Spirit, Gorman argues that the similarities in these writings express some of the most important aspects of New Testament theology and spirituality.

Although most modern scholars claim that Paul and John represent independent traditions, some have recently argued that Paul's letters influenced the later Johannine writings, while others contend that there was mutual influence. Gorman considers these proposals in light of the parallels he has examined and offers a proposal of his own that rethinks the relationship between John and Paul: Could John have influenced Paul?