John 4:24
English Standard Version (ESV)

God is spirit, and those who worship him must worship in spirit and truth.”

I love this passage so very much... I think this is the key to teaching those who are sensitive in the Spirit, and to simply dismiss those who are not, until they become so... (hahahahahaha) These are great too:

Do you love your wife and children? (How do you know you do?)
Do you have high hopes for the future? (Can we see this hope?)
Do you have faith in your friends and family? (Prove it!)
Then you can get a little more scientific:
Do you believe in Atoms - proton, neutrons, electrons - how do you know they exist if you can't see them?
If there is no Creator - what came before the Big Bang?
Does 'time' exist? You can't see or hear 'time'.

The answers to each of these we already know, which of course lead us to the answer to their doubts being obvious, too, and their doubt superfluous.

God bless you brother, great post, keep it up, Knight!