When Jesus talks to Nicodemus, he hammers home the concept of being born anew (as opposed to "again")
1: Now there was a man of the Pharisees, named Nicodemus, a ruler of the Jews.
2: This man came to Jesus by night and said to him, "Rabbi, we know that you are a teacher come from God; for no one can do these signs that you do, unless God is with him."
3: Jesus answered him, "Truly, truly, I say to you, unless one is born anew, he cannot see the kingdom of God."
4: Nicode'mus said to him, "How can a man be born when he is old? Can he enter a second time into his mother's womb and be born?"
5: Jesus answered, "Truly, truly, I say to you, unless one is born of water and the Spirit, he cannot enter the kingdom of God.
6: That which is born of the flesh is flesh, and that which is born of the Spirit is spirit.
7: Do not marvel that I said to you, `You must be born anew.'
8: The wind blows where it wills, and you hear the sound of it, but you do not know whence it comes or whither it goes; so it is with every one who is born of the Spirit."
Water and Spirit. Those are the two requisites, and those coincide with Baptism easy enough. But Nico is stuck in the imagery and concept of physical birth. He has every reason to be stuck there because that's the only "birth" he's familiar with. It's the only one I'm familiar with! Why does Christ present birth as the process for entering the kingdom of God, and yet associate birth with tangible images that are abstract and confusing?
Like with everything old, Jesus brings the new not to replace but to fulfill. And now, thanks to JPII, we should learn to look carefully at scripture when imagery and activity of the human body are present.
Human birth involves:
a. Time: human sexual impluse > conception > 40 weeks gestation > labor > birth
b. Pain: see Genesis Three Sixteen (big coincidence there) or ask your mother.
c. Water: the amniotic fluid literally floods out at some point prior to delivery
d. Blood: a birth is a messy affair
Three of these things are missing from the recipe for rebirth Jesus gave to Nico. Water is the one thing in common - Oh, and the part about a mother's womb! So what are we to think? Is it that being born anew does not require time, pain, blood and a mother? These questions are answered for Nicodemus - and the rest of us - by John later in the story.
Time - John 17
1: When Jesus had spoken these words, he lifted up his eyes to heaven and said, "Father, the hour has come; glorify thy Son that the Son may glorify thee,
A Mother - John 19
26: When Jesus saw his mother, and the disciple whom he loved standing near, he said to his mother, "Woman, behold, your son!" 27: Then he said to the disciple, "Behold, your mother!" And from that hour the disciple took her to his own home.
Pain - All of John 19
Blood (and water) - John 19
34: But one of the soldiers pierced his side with a spear, and at once there came out blood and water.
Jesus is taking on the Pain of the woman giving birth, he is delivering the new creation at the fullness of our collective 40 weeks, and what's more it is blood and water coming from his side! We are born from our mother's womb - only Eve was born from the flesh of a man. Birth into the Kingdom of God has been accomplished through Christ's Passion and the profound image of his side being pierced in the presence of John and Mary is the answer to the confusion expressed by Nico and shared by me.
Being born anew, is being born from the new Adam. Christ took care of the labor and delivery, and he left us the Spirit for everyone to reap the eternal reward of life through Him, with Him and in Him.
There is some crazy stuff in the Bible.