It is most helpful whenever God defines terms for us in scripture. Hebrews 1:14 is an example of that, as it gives us a Biblical definition of angels: “Are they not all ministering spirits, sent out to render service for the sake of those who will inherit salvation?”
In John 17:3 we find another definition, from the lips of Jesus Himself, as to what “eternal life” really is. He said: “This is eternal life, that they may know You, the only true God, and Jesus Christ whom You have sent.”
Jesus said eternal life is not just “living forever; it is not just “being in heaven”; it is not merely a “state of bliss.” It is knowing God. This is what we were created for in the beginning, and what we lost when mankind sinned and separated ourselves from God (Isaiah 59:2). This is what Jesus came to buy back for us with His death on the cross. It is through HIM, and Him only, that we may have a restored relationship with God, which is undoubtedly one of the reasons why He adds the phrase here: “and Jesus Christ whom You have sent.” Jesus is both equal with the Father, “the exact representation of His nature” — and He is also the only way we can have a renewed relationship with God (John 14:6).
Eternal life is not merely living without end. Merely extending an imperfect life forever would hardly be a great blessing — ask anyone who is miserable and suffering today. No, what makes eternal life the greatest of all treasures is knowing Him, who “from everlasting to everlasting” is God (Psalm 90:2). We will spend all eternity enjoying the pleasures and exploring the treasures of knowing Him.
And if we do know Him now through Jesus Christ, we should begin enjoying Him now by seeking Him by faith each day in His word and prayer. Yes “eternal life” lasts forever — but it begins NOW as we follow Jesus as our Savior. And let us treasure this definition which He Himself gave us: “THIS is eternal life: that they may KNOW YOU, the only true God, and Jesus Christ whom You have sent.”