I believe eternal life is a future reality—we have eternal life when we are resurrected from the dead into new bodies that will never die. Eternal life means, literally, never dying, forever living. That is our reward as followers of Jesus. Hence, we hope to “inherit eternal life” (Matt 19:29). Those who leave behind house, wife, brothers, etc. will receive many times more now and “in the age to come eternal life” (Lk 18:30). As “heirs according to the hope of eternal life” (Tit 3:7), we are “waiting for the mercy of our Lord Jesus Christ that leads to eternal life” (Jud 1:21).
Yet, it is commonly believed that eternal life begins now, when we believe in Jesus and experience new life in him. One verse that is often quoted to support this is John 17:3: “And this is eternal life, that they know you, the only true God, and Jesus Christ whom you have sent.” The problem, however, is that the Greek word for “that” is ἵνα (hina), which denotes not equivalency, but purpose. Additionally, the word “know” is in the subjunctive mood, indicating a desired outcome. Thus, Jesus is saying “this is eternal life, so that (or in order that) they might know you...” If Jesus were saying that eternal life is the same as knowing God, which the English translation can appear to be saying, then he would have more likely used the word ὅτι (hoti) and “know” would not be in the subjunctive.
This actually parallels the construction of the preceding verses: “Father, the hour has come; glorify your Son that (ἵνα) the Son may glorify (subjunctive) you, since you have given him authority over all flesh, to (ἵνα) give (subjunctive) eternal life to all whom you have given him” (Jn 17:1-2). Of course, there remains interpretive difficulty because it is not immediately clear what Jesus means when he says “this is eternal life, so that they might know you.” What exactly is being done in order that people might know God? Still, whatever Jesus means here, he is not equating eternal life to simply knowing him.
To be sure, knowing God is a wonderful thing! Right now, by faith in Christ, we can enjoy a personal relationship with God and new life in the Spirit. However, this is not our ultimate inheritance and reward. Rather, we must persevere in this faith and life in the Spirit until we obtain eternal life, when “the mortal puts on immortality” (1 Cor 15:54). Eternal life is thus the goal, the “end” of our sanctification (Rom 6:22). We live “in hope of eternal life” (Tit 1:2), which God has promised to those who believe in his Son (Jn 3:16).