Isa 29:11-12 And the vision of all is become unto you as the words of a book that is sealed, which men deliver to one that is learned, saying, Read this, I pray thee: and he saith, I cannot; for it is sealed: And the book is delivered to him that is not learned, saying, Read this, I pray thee: and he saith, I am not learned.
Another way of saying this is that the book is sealed to the one who has been taught, but not to the one who hasn’t been taught. The one who hasn’t been taught just needs to be taught.
The things that we have been taught can keep us from understanding the Bible. Any error in doctrines can keep us in error. Jesus’ prayer for unity (John 17) can’t be answered as long as we are controlled by the doctrines of our teachers.
Isaiah presented this as a paradox. The one who has been taught says he can’t read (understand) the book because it is sealed. The one who hasn’t been taught says that he can’t read (understand) it because he hasn’t been taught.
If the one who hasn’t been taught becomes taught, then the book may be sealed to him too. Even though Isaiah presented the paradox, there must be a way to solve the problem because he ended up saying:
Isa 29:24 They also that erred in spirit shall come to understanding, and they that murmured shall learn doctrine.
The one who was taught but erred will come to understand. The one who wasn’t taught because he rebelled will learn doctrine.