And where everyone (including Jesus) speaks about Spirit (AKA Holy Spirit) no one says a word about "water"...so this part must be assumed as "common knowledge" of that day and time.
Hi. I didn't read all the pages so I might be repeating what someone has already said.
Anyway, I think Jesus was addressing the assumption that because Nico was a teacher of Israel he would already understand what God wants. When Jesus said we should become like little children, I think he was suggesting that the essence of his teachings are not complex. We don't need to have the stature of teachers of Israel to be able to understand what being born again means.
Nico, with all his superior education still didn't get it and ended up saying something quite dumb (should we go back into the womb?). Like so many of us, his mind was stuck on the physical.
It is highly unlikely that the water in this reference refers to water baptism as the context of the conversation has nothing to do with baptism. This would be especially true considering John the Baptist said that he would baptize people with water but that Jesus would baptize with the holy spirit. Mt 3:11.
While Jesus' disciples baptized with water, Jesus himself did not (it's likely that, while he understood water baptism to be an OT custom, he also did not feel that it was something that needed to be forbidden) John 4:2. Paul eventually recognized that water baptism isn't what God is looking for. 1 Cor 1:17.
This is an issue of physical vs spiritual. When a woman gives birth her water breaks. It's a reference to physical birth as opposed to spiritual re-birth. That is the essence of Nico's confusion, which is illustrated by his question regarding going back into the womb.
Being born again isn't just a ritual (like water baptism). It's like becoming a baby all over again and learning an entirely new set of principles. Here's some examples.
In Matthew 23:7-12 Jesus tells the people not to use special titles like father, sir, mr, or teacher for any person on earth. In earthly culture we presumably use these titles as a sign of respect, but it doesn't take much discernment to see that it's more about pride and flattery. All you need to do is to try it and you'll see that people will quickly become very angry if they do not get the special title they think they deserve.
Another example is Jesus' teaching about working for love rather than working for money Matthew 6:24-34. He said we cannot serve two masters, with one master being God and the other master being mammon (i.e. money and the things money can buy).
Another example would be taking the lower seat Luke 14:10. In the world we are taught to go for the best. Our whole economic system is based on the idea that the more we can get for ourselves the better off we will be. Jesus says we should deliberately seek the least.
Another example is loving our enemies Matthew 5:44. In the world we're taught to fight our enemies.
Nearly every teaching of Jesus flows contrary to the values of the world. Being born again means considering these new values and actually practicing them in day-to-day life. Practicing these teachings of Jesus will necessarily cause huge divisions between us and the values of the world. We'll find it more awkward and difficult to fit in (especially regarding the money and titles issues).
But that is part of counting the cost. If you want to be a citizen of the Kingdom of Heaven you must practice the values of that Kingdom, but these values are so completely contrary to what we've known all our lives in the worldly system that learning to practice them really does require becoming like a child all over again.
Nico, with all his learning still didn't get it. He had to leave all his previous education and ideals about God behind to learn something completely new. The same will be true for any one of us today.