Eternal means FOREVER and EVER.
You seem to be the naive one.
Joh 5:24 KJV Verily, verily, I say unto you, He that heareth my word, and believeth on him that sent me, hath everlasting life, and shall not come into condemnation; but is passed from death unto life.
I guess that, according you, someone can continually PASS from DEATH UNTO LIFE and back UNTO DEATH ..... again and again and again......
You are making eternal life into an
endless extention of OUR existence which we obtain
once for all and
possess thereafter without condition as an
attribute of our being. In the scriptures eternal life resides IN the Son. We receive it on an
ongoing basis from Him as we
abide in Him. It is not a blessing we can enjoy apart from ongoing union with Him.
The need to actively abide in Christ is expressed in
John 15:4-5 where Jesus is shown to be the Vine. "Abide in me" He said. "Abide in" means, "dwell in," "remain in," "continue in" Through maintaining this
faith relationship we continue to receive life-giving "sap" from the vine, and enjoy HIS life which has the property of being eternal. The life we have is derivative. We receive it conditionally by
continuing in the faith.
That this IS how eternal life is received and experienced is shown by the following verse:
IF what you
heard from the beginning
abides (remains, continues) in you, you also will abide
(remain, continue) in the Son and in the Father.
And THIS is the promise that he made to us—eternal life (
1 John 2:24-25).
The promise of eternal life is unconditional. Its continuance in us depends on our continuing in the truth of the Gospel. According to this verse
if we do not continue in the teachings of the Faith we will not stay in the flow of His life.
You asked whether a person who has passed into life can pass out of it again. There are many sciptures that address this. One is here:
6 If anyone
does not abide in me he is
thrown away like a branch and
withers; and the branches are gathered, thrown into the fire, and
burned (
John 15:6).
This refers to a person who was connected to the vine but who does not remain there. Withering is the slow desiccation that occurs after a branch has separated itself from the vine. Eventually, when it is completely dry it is gathered up and burned. These individuals can return until their heart becomes so hardened that they do not want to which is the sin of Apostasy. Jude calls individuals like this "twice dead" meaning that they were dead initially (as unbelievers) but that they subsequently died again so they were "twice dead." I do not think God does not has a numerical quota of how many times he will restore a lapsed believer to repentance. In time, however, their heart will become so hardened that they WILL not repent.
We do not really
own eternal life. Eternal life is a property of God alone (
1 Tim 6:16) which He has given to reside in the Son (
John 5:26). We only borrow it from the Son as we abide in Him.
All the descriptors of the new life describe it not as a static state but as something ongoing and in
motion
The water of (eternal) life given to the Christian to drink is the Holy Spirit of Life (
John 7:38-39). We become alive initially by that drink but subsequently that drink becomes a well of water "
springing up" inside us unto
eternal life (
John 4:14). Eternal life is shown to be something we must
continue to drink.
Eternal life is also compared to manna which did not come once but every day. They could not even store the manna over night. After comparing Himself to this "bread from heaven" Jesus explains how the new life is experienced:
57 As the living Father sent me, and
I LIVE because of the Father, so whoever
feeds on me (continually),
he also will live because of me. 58 This is the bread that came down from heaven, not like the bread the fathers ate, and died. Whoever feeds
(continually) on this bread
will live forever” (
John 6:57)
To live forever we must
stay connected to our Source of life. Jesus says here that His own
source of life as a human being was not in and of Himself. He lived
BY the Father, that is, it was
THROUGH union with and dependence upon God that He enjoyed the Father's own life. (Eternal) Life was not something He enjoyed apart from active union with the Father.
Jesus' walk involved pleasing the Father. He said "I do always what pleases the Father." We are to live
BY Jesus the same way He lived
BY the Father. AS we do we enjoy Christ's life just as He did the Father's.
That
eternal life is more than simply an
endless extension of our own existence can be seen here (
John 17:3) The word "know" here means to
know relationally. Eternal life is personal relationship and communion with Him.
The common mistake, I believe is to make eternal life either a
static legal status or a
deposit of Divine essence. Eternal life is derivative. It is borrowed from Him. We do not have it as a permanent feature of our existence. We cannot earn it. We do not deserve it. We can only share it with Him as we walk with Him in faith. AS long as we abide there we enjoy the eternality that is a quality of His life.