But there is an intellectual process. To totally deny any use of the brain is insane.
The brain is not the issue, the mind is. The brain is just the physical interface between our minds (spirits) and the flesh (physical world). You can scramble the brain, but the mind remains as spirit.
The knowledge is given to our spirit when we receive saving faith. When our brain hears the gospel, a connection is made between those words and the spiritual knowledge that is a gift from the Spirit. Saving faith does not depend on the ability of the brain. A properly functioning brain helps us confirm that we have been given saving faith.
No matter the condition of the brain, it is the mind that believes. It is our spirit that has saving faith. Infants and mentally retarded people still have perfectly functioning spirits that can be saved by God's grace.