Faith requires spiritual understanding, but yet we by nature prior to regeneration are described here Eph 4:18
18 Having the understanding darkened, being alienated from the life of God through the ignorance that is in them, because of the blindness of their heart:
Now Faith comes by hearing and understanding the word spiritually Matt 13:23
23 But he that received seed into the good ground is he that heareth the word, and understandeth it; which also beareth fruit, and bringeth forth, some an hundredfold, some sixty, some thirty.