Why is the excuse 'I can't understand the Bible' not valid?
Claiming inability to understand Scripture fails because the Bible is not that difficult. Every believer can simply get into the Book and feast on it. Understanding comes by comparing Scripture with Scripture, recognizing that God dealt with the Jew under Law while dealing with us today under Grace.
Les explains that the same principle applies today: every believer can get into the Book and feast on it, but most won't. When someone offers the excuse, "I can't understand it," Les responds that they can—it is not that difficult. His first premise is to separate what is for the Jew and what is for the Gentile, not to throw aside the Jewish portion, but to compare Scripture with Scripture in light of the fact that God dealt with the Jew under Law and deals with us today under Grace. Law and Grace are two totally contrary principles and will not mix. Paul also cries against legalism in any form, because believers are not under Law but under Grace.