This book contains her original work Spiritualism in the Light of Occult Science with commentaries by Gareth Knight. As well as being an occultist of the first rank, Dion Fortune was an accomplished medium. Thus she is able to explain the methods, technicalities and practical problems of trance mediumship from first hand experience. She describes exactly what it feels like to go into trance and the different types of being one may meet with beyond the usual spirit guides. For most of her life, her mediumistic abilities were known only to her immediate circle until, in the war years, she responded to the call to try to make a united front of occultists and spiritualists against the forces of materialism in the post-war world. At this point she wrote various articles for the spiritualist press and appeared as a speaker on several spiritualist platforms. This book contains her original work Spiritualism in the Light of Occult Science with commentaries by Gareth Knight that quote extensively from now largely unobtainable material that she wrote on the subject during her life, including transcripts from her own trance work and rare articles from old magazines and journals. Dion Fortune needs no introduction to the student of the Western Esoteric Tradition as the founder of a major occult school, the Society of the Inner Light. Gareth Knight, originally a student of her school, after making a name of his own as an esoteric author and teacher, has recently returned to the Society. This book represents the fourth collaborative work between the two, An Introduction to Ritual Magic, the Circuit of Force, and Principles of Hermetic Philosophy being already published in this series.