Altered States of Consciousness

Whenever I speak on the topic of dreams, I mention a very unusual sort of dream, the "lucid" dream (see Chapter 8) in which the dreamer knows he is dreaming and feels fully conscious in the dream itself. After discussing some of the philosophical and semantic difficulties in defining states of consciousness, I always ask whether anyone has the slightest doubt that he is awake, that is, in a "normal" state of consciousness at that moment; I have never found anyone who had difficulty in making this distinction.
In introducing a book of readings on altered states of consciousness, I find myself in a similar position: there is a multitude of philosophical and semantic problems in defining just what "normal" consciousness and "altered" states of consciousness are, yet at this instant I have not the slightest doubt that I am in my normal state of consciousness. Yet there have been a number of occasions in my life when I have not had the slightest difficulty in realizing that I was in an altered state of consciousness (ASC). Thus I shall give only the simplest sort of definition of what an ASC is here and let the articles in this book flesh it out: our knowledge of ASCs is too incomplete at this time for a tight conceptualization.