The term eternal life is a central theme found in the Gospel of John. The very purpose of John's gospel was that "you may believe that Jesus is the Christ, the Son of God, and that by believing you may have life in his name" (Jn 20:31; cf. 1 Jn 5:13), "life" being synonymous with "eternal life". Jesus says that, "this is eternal life: that they may know you, the only true God, and Jesus Christ, whom you have sent" (John 17:3). Interesting to note, knowing God does not precede or follow eternal life. Instead, knowing God is eternal life. "Those who know God in the present have an incorruptible fellowship with God that cannot be severed or impugned by death" (Thompson, p. 380). Furthermore, Jesus says that "I have come that they may have life, and have it to the full." Marshall believes that "the most comprehensive term in John for what Jesus gives to people is life or eternal life, which is to be understood as sharing in the life of God [John 1:4] (Marshall, p. 520).Thus, understanding the term eternal life is of great importance to the Christian life.
Scholars have speculated on John's usage of "eternal life" as opposed to the Synoptic Gospel's use of of " Kingdom of God". Some suggest that John uses this term "to accent the personal and individualistic aspects of salvation". On the other hand, some believe that his use conveys "the inner experience of salvation more aptly than a term like kingdom of God" (Thompson). However, the Synoptics do in fact use the terms eternal life and kingdom of God as equivalent terms (Mk 9:43, 45, 47; 10:17-30; Matt 19:23-29; Luke 18:24-30), and so they are to be understood as synonymous terms.
The background of the term is to be seen in light of first century Jewish thought. Jews had a vision of the "life of the age to come" that the righteous were to inherit. Scholars believe that John picks up on this idea, equating "eternal life" with this very idea so that it is understood as "the state of blessedness that one participates in through faith in Jesus" (Thompson). Furthermore, Jesus said to the Jews, "You diligently study the Scriptures because you think that by them you possess eternal life. These are the Scriptures that testify about me, yet you refuse to come to me to have life" (Jn 5:39-40). Ladd writes that "it was commonplace in rabbinic teachings that the study of the Torah would lead to "life in the Age to Come" (p. 292).
Eternal life and the future
A striking reality is that John's gospel presents salvation, or eternal life, in the present tense (Jn 5:24-26). Although it may appear odd to have the "life of the age to come" in the present, John's gospel presents aspects of this idea, sometimes known as realized eschatology. The term is used to convey the idea that aspects of the end times are present now with believers. John's gospel does not put forth this view in its entirety, instead, it simply finds greater emphasis than in other books of the New Testament. Jesus has come down from heaven to give life now (Jn 6:33), for his words are life (Jn 6:63),the Father's commands lead to eternal life (Jn 12:49-50), and even Jesus himself can say "I am the life" (Jn 11:25; 14:6). Yet, one of John's best known images for the presence of salvation is the term "born again" (Jn 3:5-21; cf. Jn 1:13). This conveys the idea that people are without life until they receive the divine gift, a gift that can be received and experienced in the present (Marshall, p. 520).
The eschatological character of John's usage of eternal life is also evident in Jesus' saying, "The man who loves his life will lose it, while the man who hates his life in this world will keep it for eternal life" (Jn 12:25). This saying marks the understanding of two ages, this age and the age to come (Ladd, p. 293; cf. Daniel 12:2). The life is eternal in that those who receive it will never perish (Jn 3:16; 6:27; 10:28).
“The ‘race set before us’ is an uncommon foot race, for the victor’s wreath of life that we pursue is the life that already courses through our mortal bodies by God’s Spirit (Romans 8:11). This is not the rhetoric of a sports commentator reporting on the marathon at the Olympics: ‘The runners are already empowered by the gold.’ It is much more than desire for the gold that invigorates runners in this uncommon race. For we are affirmed that although eternal life is God’s prize of salvation that we pursue with eager hope, eternal life is also the gift of grace that already invigorates us with the resurrection life so that we run the race with perseverance. Eternal life is the reward that we trust God will give to us who faithfully endure to the end of the race. Yet eternal life is also the very breath of heaven that already fills our hearts by God’s Spirit and enlivens our ‘feeble arms and weak knees’ (Hebrews 12:12) to ‘run the race set before us’ (Hebrews 12:1).” - The Race Set Before Us: A Biblical Theology of Perseverance & Assurance, by Ardel Caneday and Thomas Schreiner, p. 88
- M. M. Thompson, "John, Gospel of" in Jesus and the Gospels, ed. by Joel Green & Scot McKnight (IVP, 1992)
- George Ladd, A Theology of the New Testament (Eerdmans, 1993)
- I. Howard Marshall, New Testament Theology (IVP, 2004)