You are in front of the TV, watching soccer.
Your neighbour shouts, "GOAL!!!"
You're puzzled: no goal has been scored!
You hiss.
He's probably drunk or something.
20 minutes later, he yells, "GOAL!" again!
He starts blowing his vuvuzela to celebrate.
You go knock on his door...

He opens the door, you see a dozen guy celebrating.
You look at the TV. Then it hits you:
They are watching Real Madrid against Barcelona!
No wonder the shouts of goal didn't make sense to you: you were watching Chelsea against United!
You're not tuned to the same station!

So it is with spiritual things.
God is a Spirit.
That is like a TV station, say, CNN.
You are flesh.
Another TV station, say BBC.
For you to know what is happening in CNN, YOU HAVE TO TUNE TO THE STATION!
As long as your TV is on BBC, you won't know, else you're told...