Hebrews 11:1 Now faith is the substance of things hoped for, the evidence of things not seen.

Faith is substance.  It isn't a blind acceptance of something.  It isn't a mental exercise.  It's not based on what we can prove scientifically.  It is a spiritual substance.

It has the power to move mountains, not by human effort but by God's Hand.

Faith is actual evidence in the spiritual realm. 

The secularists, like the Greeks, cannot understand faith.  It seems like foolishness to them because of their blindness and their preconceptions.  They ask for the evidence.  They want to debate faith.  God simply declares, "I am."