When Adam and Eve sinned, they, representing all mankind, were expelled by God from the Garden of Eden. The Garden represents being in God's presence and thereby having easy access and communication with Him. In Genesis 2:17, God had warned Adam and Eve that in the day they ate from the Tree of the Knowledge of Good and Evil, they would die. Once they sinned, it became evident that God did not mean they would die immediately, but that, if they ate of that tree, they were as good as dead.
Their human life went on, but God, to emphasize the serious effect of their sin to later generations, placed a flaming sword to guard the Garden's borders. This portrayed that mankind, though still alive, was cut off from any relationship with Him. Thus, sin, which demonstrates a lack of love and fidelity for our Creator, not only seals the death penalty on each sinner, but it also denies an individual access to and thus communication with God while he lives on under Satan's continuing influence.
When Jesus paid the penalty for our sins, and we, by faith in that sacrifice, became justified, God legally cleared us of guilt before Him. It is as though the barrier of the flaming sword between us and Him were removed, opening the way for communication with Him and for the growth of a relationship with Him that never before existed for us.
The relationship we have with the Father and the Son through the work of Jesus Christ, both as the payment for our sins and as our High Priest, is everything in terms of salvation. Why is this true? Because we can now communicate with Them! Having access to God furnishes an opportunity for a relationship with the Father and the Son. The relationship is the medium of communication - holy, righteous, spiritual communication.
This communication is more than a mere counterbalance to the evil spiritual influence of this world. It decidedly tips the scales in our favor in this war for our spiritual survival, if we will but continue to believe and trust Them by taking advantage of the contact, communication, and influence freely given to us. What Jesus does ever so briefly in John 17:3 is to tie quality of life, called "eternal life," to a person's relationship with God.
Even though many in it may be religious, the world does not have a relationship with God. There is no communication from Him to them. Undoubtedly, a lot of people know many things about God, but they cannot actually know Him without access to Him. It is like a person knowing of someone from across town by reputation but really knowing nothing about him through personal contact.
