Picture two lines. One runs across the page: everything you know. The other runs up the page: everything you are. How patient you are. How honest. How kind you are when you are tired.
Most of life feeds the first line. School, books, the news, a thousand videos. The line of knowing grows and grows, and the line of being hardly moves. That is why a person can know a great deal about anger and still shout at their children. The knowing never reached the being.
The tradition calls the second line the level of being. Your life is shaped far more by it than by what you know. Your relationships, your nights, even the events that seem to happen to you tend to match the level of the person they happen to.
This book feeds both lines, but it cares most about the second. Every idea here is worth only what it changes in you. If you finish a page and are only better informed, the page has half failed. If you finish a page and act differently by evening, it has done its work.
The two lines meet in one place: understanding. Understanding is knowledge that has become part of what you are.