Chapter 5 was entitled "Consciousness" and dealt with the biology of sleep, dreams, hallucinations, out-of-body and near-death experiences, déjà vu, etc. It also discussed different types of drugs and their effects on the mind. It basically dealt with all things with the brain when it is not in its normal, alert state. I found it very interesting. In particular, I found the section on déjà vu interesting.
Déjà vu is the strange sensation one feels when they believe they have already experienced something. One possible theory on why this happens states that someone may be experiencing something that is very similar to a previous experience. The mind subconsciously remembers a previous experience, but a person cannot put their finger on actually experiencing it. So, they feel like they have already experienced something, but they cannot remember doing so. What are some recent experiences of déjà vu you can recall?