Can unbelievers understand deep Bible doctrine?
No. Paul writes that the natural man, the unsaved person, receiveth not the things of the Spirit of God. An unbeliever may understand a few simple things, such as the story of Bethlehem, but deep doctrinal aspects of the Word and end-time prophecies remain a closed book because these things are spiritually discerned.
Les explains that although believers can understand the Scriptures and compare Scripture with Scripture, the unsaved person cannot do that; he cannot see where these things are connected. Paul calls the unsaved person the natural man, who receiveth not the things of the Spirit of God. Les says maybe unbelievers can understand a few things, such as the story of Bethlehem, but when it comes to the deep doctrinal aspects of the Word of God, it is a closed book. End-time prophecies are also a closed book to them. Why? They do not comprehend because they do not want to; it is all foolishness to them. Consequently, because all of this is foolishness to the unbeliever, he cannot know them, since these things are spiritually discerned or understood.