The word 'hallucinogens' is commonly used to classify LSD and similar drugs, but it is vague and sometimes confusing. A more clinically precise classification, proposed by Jean Delay in 1959, categorizes these substances as psychodysleptics because they disturb mental activity and distort a person's judgment of reality. This classification implicitly acknowledges that cultural definitions of reality shape the drug experience. Despite this precision, the authors choose to use the term 'hallucinogen' for literary reasons.
Occultism in Germany around 1900 was not a fringe rejection of science but a serious intellectual movement that helped shape modern German culture. The book traces how figures from psychical researchers, artists, and writers engaged with occult ideas to explore questions of mind, matter, and spirituality. These pursuits influenced the development of psychology, the arts, and alternative religious movements. The author argues that occultism provided a 'science for the soul' that addressed anxieties about materialism and offered a bridge between scientific rationality and spiritual experience, contributing to the emergence of German modernism.