We speak about faith things as if we are insane. Paul surely felt this to be true.
Kingdom life and church action are not conducive to the business mind. It's nuts, really. II Cor. 2:14 insists that natural minds cannot grasp the things of God. Rather, they assume them to be foolish.
The church struggles in large part today because we are trying to walk with one foot in heaven and one on earth. We like the promises while disdaining the disciplines. The old rugged cross for most is a song; not a march.
Jesus did not first call us to go to heaven. Rather he first brought heaven to earth and said, take a look. He defied natural thinking to the extent mankind remains perplexed and baffled. We still see as in a mirror dimly.
It was when Jesus died on the cross that the curtain was split in the temple. That very curtain had kept heaven at bay...or us depending on how you look at it. Only the high priest dared enter. None other. When the curtain ripped, heaven came out. It wasn't torn that man could enter; but rather that God could exit. God could now interact with us in Spirit as heaven was moving in.
With the Spirit of God being poured out at Pentecost, the heaven and earth traffic really picked up. We co-labor with God, worship Him, and perpetually ask Him to send in wisdom from above. The heaven and earth interaction is fascinating.
To the unbeliever this is simply a figment of the imagination; seemingly without ever considering where in the world they got an imagination in the first place.