In chapter 5, the author introduced a concept called lucid dreaming, which is defined as experience of becoming aware that one is dreaming (Page 171, Lilienfeld textbook, lucid dreaming). It challenged the idea that people are either totally asleep or totally awake. According to the textbook, most of people have experienced lucid dreaming. More that 70% of people believe they can control their dreams.
In my opinion, lucid dreaming can be interpreted as the grey area between total asleep and total awake. It is common in our daily lives. For example, my Mom has been having lucid dream for a long time, and she often described her dreams as partially related to her real life experience. For example, she will dream about cooking at her kitchen. She might wake up and realized it was a dream, but later she would continue the dream. It seems that she was telling a story, and suddenly the story was stopped when she realized she was dreaming, and then she fell asleep again and the story continued.
I have experienced lucid dreaming for many times. Especially after I played basketball. I got excited about the game and would think about it when going to bed. When I fell asleep, I often dreamed about playing basketball, and during the dream when I jump for a rebound I often kicked my legs in bed, sometimes it woke me up and made me realized that it was a dream, but later I usually continued sleeping with the same dream. In addition to the dreams of sports, I experienced lucid dreaming when I have nightmares and dreams of violence. The scary content of the dreams woke me up, but I could not get up from my bed. I would know it was a dream, and I would fell asleep again continued the same dream. I tried to control the dream sometimes when it is scary, but usually it did not work.
I think the concept of lucid dream is very important for the reason that it opens up the possibility of controlling our dreams. There are a couple of times when I have nightmares I could control my mind and told myself it was only a dream and felt peaceful. However, I have not successfully got up from bed when I realized I was having a nightmare. I believe it is possible to control one's dream with some practice.
In addition, based on the scientific thinking principle #4 of replicability (Page 23, Lilienfeld textbook, scientific thinking principle #4), if the assumption that we can control our dreams is correct, we need to do further experiments to get the same results to show that it can be replicated. My personally experience of controlling my dream can be led by a fluke.