The human mind cannot understand spiritual things. Paul explains this in
1 Corinthians 2:14 (NASB):
"But a natural person does not accept the things of the Spirit of God, for they are foolishness to him; and he cannot understand them, because they are spiritually discerned."
No one can understand the Bible with their mind alone. The Holy Spirit is given to us and lives in us to lead and guide us into spiritual truth.
Our spirit informs our mind. That’s the only way a person can understand God or the Bible—when the Holy Spirit reveals it to us.
In John 16:13, Jesus says:
"But when He, the Spirit of truth, comes, He will guide you into all the truth. He will not speak on His own; He will speak only what He hears, and He will tell you what is yet to come."