Only those who have received spiritual insight can know Christ personally and come to trust in Him.

“It is written in the prophets, ‘And they shall all be taught by God.’ Therefore everyone who has heard and learned from the Father comes to Me.” (John 6:45)

Now a certain woman named Lydia heard [us]. She was a seller of purple from the city of Thyatira, who worshiped God. The Lord opened her heart to heed the things spoken by Paul. (Acts 16:14)

Whose minds the god of this age has blinded, who do not believe, lest the light of the gospel of the glory of Christ, who is the image of God, should shine on them. For we do not preach ourselves, but Christ Jesus the Lord, and ourselves your bondservants for Jesus’ sake. For it is the God who commanded light to shine out of darkness, who has shone in our hearts to give the light of the knowledge of the glory of God in the face of Jesus Christ. (2 Corinthians 4:4-6)

And we know that the Son of God has come and has given us an understanding, that we may know Him who is true; and we are in Him who is true, in His Son Jesus Christ. This is the true God and eternal life. (1 John 5:20)

If by spiritual revelation only can one understand God, His person, purpose, and ways, why should the Scriptures spend undue time and ink trying to persuade spiritually blind men something they cannot accept? The Bible works from the position of assuming His existence and leaving men to believe what they choose. And without God granting special revelation to the sinner, the sinner will never experience the person of God in a righteous way.