Why can believers compare Scripture with Scripture but unsaved people cannot?
Believers can compare Scripture with Scripture because they have spiritual discernment, while the natural, unsaved person cannot receive or comprehend the things of the Spirit of God. Such truths are foolishness to him and are spiritually discerned, leaving deep doctrine and prophecy a closed book.
Les teaches that believers can understand the Scriptures and compare Scripture with Scripture, but the unsaved person cannot do that and cannot see where these things are connected. Paul calls the unsaved person the natural man, and the natural man receiveth not the things of the Spirit of God. Les explains that an unbeliever may understand a few things, perhaps 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 closed to them. The reason he does not comprehend is that he does not want to, and it is all foolishness to him. Unsaved neighbors may think something is wrong with you for going to a weeknight Bible study. Since all of this is foolishness to the unbeliever, he cannot know these things because they are spiritually discerned or understood.