In John 15:1-8, Christ used vines and branches as a teaching tool. There were a few things that He brought up in this illustration that is important to mention. These teachings of Christ should have a strong bearing on what we believe about Salvation, Discipleship and Eternal Security.
When Christ mentions in verse 5 "...apart from me you can do nothing," Christ is talking about salvation. Without Christ in the center of everything, we cannot grow. Without Christ in the center of a marriage or family it will wither the same way a grape will wither off a vine. Apart from that vine, the branches will fall. Christ is our way to the Gardener, and that is God. The only way to get to the Gardner is through the vine. Jesus referred to Himself as the vine and as Elmer Towns puts it in The Gospel of John: Believe and Live, "When Jesus called Himself "the true vine", He was drawing on an obvious parallel."1 Christ wanted people to know that He was referring to Himself as the only way to get to God.
While not as obvious as Salvation, Discipleship is a major part of this passage. Christ says in Verse 15:2 that "He cuts off every branch in me that bears no fruit, while every branch that does bear fruit he prunes so that it will be even more fruitful." We as Christians are to be disciples to the world. As Leon Morris says in Jesus is the Christ: Studies in the Theology of John "The purpose of growing vines is to produce grapes, not foliage."2 The reason the Gardner, God, prunes us is that we might produce fruit. If we are not producing fruit, we are useless and He will cut us off from His blessings. That is the main reason we are here, we are given The Great Commission as God's children.
The last thing that Christ brings up in this passage is about our eternal security. This is a much debated subject within the Christian church. There are even many colleges that will teach pastors that you can lose your salvation. Many use this passage as a way to say that Christ will cut you off and you are away from God. While I believe that this is what Christ is saying, I don't believe he is referring to our salvation. If you think of a branch on a vine, you know that once you cut off a dead branch or trim a branch, it will grow back and it can once again produce fruit. A dead branch will not produce any fruit. So, Christ is saying that He will cut you off from the blessings of the Gardner, but you are still a part of that plant, just not connected to God. We need to stay connected to God and keep producing fruit to receive God's blessings through the vine. Also, Christ could be referring to unsaved "believers," those who say they believe and say all the right things. Sam Storms puts it good when he says "The view that the fruitless branches are unregenerate is supported by what John's gospel says about unsaved believers. In other words, John often portrays people as "believing" in Jesus who clearly are not born again."3
While Christ used many ways to teach, metaphors can often be used out of context. When using Christ's words for teaching, you often have to use other Scripture to help your point of view. There are many verses in the Word that guarantee our eternal salvation. See http://bible.org/seriespage/assurance-eternal-security for more information. It is a great site to check out.
1. Towns, Elmer. The Gospel of John: Believe and Live. Scofield Ministries.2002. Page 150
2. Morris, Leon. Jesus is the Christ: Studies in the Theology of John. Wm. B. Eerdmans Publishing Company. 1989. Page 121.
3. Storms, Sam. John 15:1-6 and the Security of the Believer. Nov. 7, 2006. Enjoying God Ministries.