This is an excerpt from my free eBook Am I Flexible or Focused?

I believe that the gospel of John has a dual purpose. 

Many have called John 20:30-31 the purpose statement for the Gospel of John. I believe this is right, but it’s important to note what John didn’t say. He didn’t say he wrote his Gospel “to ONLY teach how to have ETERNAL life.” 

Instead he said, “…by believing you may have life in his name.”

It seems significant to me that after using the term “Eternal life” so many times in chapter 1-12, that he doesn’t say that his Gospel is ONLY to teach us how to have ETERNAL life, but instead the more generalized LIFE, which could include Eternal life but also include Abundant life (John 10:10). I think this is a reference to the fact that Jesus came to teach us how to have two types of life: Eternal Life, and Abundant Life. Likewise, I believe that John’s Gospel has that same dual purpose. 

I believe John 10:10 is the key to understanding John 20:30-31. 

First Jesus said he came to give life [eternal]. I believe that roughly John chapter 1-12 is the section in which John relays Jesus’ teaching on the subject. This is his salvation material. 

Secondly Jesus said he came to give life more abundantly. I believe that roughly John chapter 13-21 is the section in which John relays Jesus’ teaching on how to have an abundant life. This is his discipleship material. 

There is a noticeable dividing point in the gospel of John that comes between chapter 12 and 13. Before 12 Jesus is largely trying to convince unbelievers to believe so that they can have eternal life. 13 and beyond, Jesus is mostly teaching his disciples who had already believed, and now needed to learn to to abide, obey, and continue in the faith so that they could have abundant life. 

I’m convinced that John sets up Jesus’ later-chapter discussion on discipleship in chapter eight:

As He spoke these words, many believed in Him. Then Jesus said to those Jews who believed Him, “If you abide in My word, you are My disciples indeed. (John 8:30–31)

He associates Discipleship with Abiding. Then in chapter fourteen, he brings it up. In chapter fifteen he talks extensively about abiding. He mentions it ten times. He continued for the next few chapters to talk about the Holy Spirit, Unity, Prayer, and Loving one another to show the world Jesus’ love. There’s just no question in my mind. The gospel of John has long passages about discipleship. It’s embedded in his purpose for writing. 

The idea that the Gospel of John has a discipleship purpose in addition to its evangelistic purpose should not be controversial. 2 Timothy 3:16 says, “All Scripture is God-breathed and is useful for teaching, rebuking, correcting and training in righteousness…” Those are discipleship-related issues, and they apply to all Scripture. Thus, John has a discipleship purpose in addition to his evangelistic purpose.

I think John’s first 12 chapters are unique in the Bible. Coupled with the fact that he expresses his purpose as giving life by belief (John 20:30-31), I’m confident that we can treat John 1-12 as a specifically evangelistic segment of Scripture. However, I believe we need to be careful not to imply that John has no other purpose. 

So John’s Gospel is written to both unbelievers and believers. For unbelievers, it’s a manual on how to get eternal life. For those who have believed already, it is a manual on how to make that life abundant by abiding, obeying, and continuing in the faith. 

Is the saving message found anywhere outside of John's Gospel?

While I believe John 1-12 is a uniquely evangelistic segment of Scripture, and I’d prefer to use it for evangelism, I admit it’s not the only place in the Bible that contains a saving message. I made this point years ago in my book Eternal Life, by pointing out a passage in Romans, though I indicated my preference for John’s Gospel, since Romans is written in a much more complex language. 

So, I believe the saving message is present in other Biblical books apart from John. While it may not be the primary purpose of the writers of other biblical books, Some examples of the saving message in non-John books include Acts 13:38-39, 16:29-31, Romans 3:22-24, Galatians 2:16, Ephesians 2:8-9, 1 Corinthians 15, and probably a handful more. 

While my preference is to use the first half of the Gospel of John as my sole evangelistic content, I do not intend to divide from those who take a different approach. Many have received salvation by reading non-John books in the Bible. I do not wish to stifle the multiplicity of ways God has used evangelists to bring others to belief in Jesus. 

This does not mean that all evangelistic approaches are acceptable; far from it. However, I do not seek to criticize those who are able to do faith-alone evangelism from books other than John, provided that in using the non-John approach, they are committed to being clear and coherent about the simple requirement for receiving eternal life. 

This is an excerpt from my free eBook Am I Flexible or Focused?