" The witness is in the hidden regions of the spirit, too deep for proof, where external evidence is invalid and “signs” are of no use. When all is said, it may easily be that the great difference between professing Christians (the important difference in this day) is … between those who have reduced Christianity to an intellectual formula and those who believe that the true essence of our faith lies in the supernatural workings of the Spirit in a region of the soul not accessible to mere reason. "
― A.W. Tozer , Tozer on the Holy Spirit: A 365-Day Devotional