In this book J. Allan Hobson offers a new understanding of altered states of consciousness based on knowledge of how our brain chemistry is balanced when we are awake and how that balance shifts when we fall asleep and dream. He draws on recent research that enables us to explain how psychedelic drugs work to disturb that balance and how similar imbalances may cause depression and schizophrenia. He also draws on work that expands our understanding of how certain drugs can correct imbalances and restore the brain's natural equilibrium.