Herbert Silberer was a Viennese psychoanalyst involved with the professional circle surrounding Sigmund Freud which included other pioneers of psychological study as Carl Jung, Alfred Adler and others. He had a background in athletics and sports journalism.He was very interested in dreams, and in 1909 published a paper detailing his research into the hypnagogic state (the mental state in which the individual is between waking and sleeping). Silberer's contention was that the hypnagogic state is autosymbolic, meaning that the images and symbols perceived in the hypnagogic state are representative (i.e. symbolic) of the physical or mental state of the perceiver. He concluded that two "antagonistic elements" were required for autosymbolic phenomena to manifest: drowsiness and an effort to think.In 1914, Silberer wrote a book on the relationship between modern psychology, mysticism and esoteric traditions (particularly Western, Christian ones such as Hermeticism, Alchemy, Rosicrucianism and Freemasonry): Probleme der Mystik und ihrer Symbolik (Problems of Mysticism and its Symbolism). Many of the insights Silberer offered, especially into the link between alchemical imagery and modern psychology were similar to those developed more extensively by Carl Jung, a fact acknowledged by Jung in his seminal work on the subject, Psychology and Alchemy. Silberer's book was coldly rejected by Freud. Silberer became despondent and later committed suicide by hanging himself after being excommunicated from Freud's circle of associates.