Overview

Physical mediumship encompasses a diverse range of allegedly paranormal phenomena purportedly produced through a medium’s agency in séance settings. Nahm’s work in this domain spans historical scholarship, direct participatory observation, and critical analysis of contemporary claims. His approach combines archival research with firsthand investigation, allowing him to situate modern phenomena within broader historical contexts while maintaining rigorous skepticism toward unsubstantiated claims.

The phenomena traditionally associated with physical mediumship are extensive. They include audible raps and knocks originating from tables, walls, or ceilings; unusual movements and levitations of objects; various luminous phenomena; materializations of white substance termed ectoplasm; manifestations of human hands or full apparitions; and apports, the unexplained appearance of physical objects.¹ These phenomena have been reported across centuries and continents, generating both scientific interest and skeptical scrutiny.

Historical case analysis

Nahm’s historical work reveals that interpretive frameworks for understanding mediumship developed earlier and more diversely than conventional accounts suggest. In collaboration with Carlos Alvarado and Andreas Sommer, Nahm documented that ideas invoking human agency (rather than discarnate spirits) to explain mediumistic phenomena appeared in the early mesmeric and spiritualistic literature, predating the Society for Psychical Research’s founding in 1882. Writers including Carl Gustav Carus, Edward W. Cox, Justinus Kerner, and others proposed that mediums might obtain information through telepathy, clairvoyance, or other psychic abilities rather than through spirit communication.² This historical perspective complicates narratives attributing such explanatory innovations solely to late-19th-century researchers.

Nahm’s examination of specific historical cases illustrates the interpretive complexities surrounding physical mediumship. His analysis of Carlos Mirabelli’s mediumship, a Brazilian medium active in the early 20th century, exemplifies this challenge. Mirabelli was simultaneously hailed as an outstanding genuine medium by some observers and regarded as a complete fraud by others. Nahm presents historical material contextualizing the famous 1928 visit of biologist and philosopher Hans Driesch to Mirabelli’s séances, along with accounts of sittings held in New York in 1930 and 1935.⁵ These cases demonstrate that even when credible witnesses document phenomena, disagreement persists regarding their authenticity and explanation.

Contemporary circle investigations

Nahm’s most extensive contemporary investigation involved the Felix Experimental Group (FEG), a circle for physical mediumship established in Hanau, Germany, in October 2005 under the direction of medium Kai Mügge. Over four and a half years, Nahm participated in 21 sittings, observing phenomena including unusual table movements, raps on walls and ceilings, luminous and psychokinetic phenomena, ectoplasm generation, and apports.¹

Nahm’s involvement in the FEG circle evolved from initial openness to documented skepticism. He describes the controls applied during sittings and his personal role in accompanying the circle’s development. Crucially, Nahm arrived at the conclusion that considerable portions of the phenomena were produced by fraudulent means. His investigation identified specific instances of deception: Mügge used a magician’s LED device to produce a red “spirit” light, and he generated self-luminous ectoplasm using Halloween spider web material while pretending to be in trance.¹

The evidence for Mügge’s fraud was substantial. Nahm documented 109 photographs showing Mügge’s use of the LED device during séances. The device was discovered in Mügge’s travel bag by the circle’s former leader, Jochen Soederling, and Mügge admitted to Soederling in a telephone conversation on April 2, 2014, that he had used this device.³ These findings underscore the importance of sustained, critical observation in physical mediumship research.

Methodological critique and fraud detection

Nahm has contributed significantly to methodological discussions in physical mediumship research through critical analysis of contemporary investigative approaches. A notable example is his commentary on Eckhard Kruse’s audio signal processing analysis of alleged “spirit voices” recorded during séances with medium Warren Caylor. Kruse, a professor of applied informatics, analyzed voice recordings using multiple microphones positioned in the séance room to localize voice sources and examine voice characteristics, particularly formants, amplitude peaks in the frequency spectrum determined by individual vocal tract anatomy.⁴

Kruse argued that formants F3 and F4 are difficult to alter even when people dramatically disguise their voices, and that their alleged immutability represents an important feature of voice forensics. Based on recordings showing considerable differences in F3 and F4, Kruse concluded that Caylor’s “spirit voices” were genuine and that his measurements excluded all possibilities of fraudulent production.⁴

Nahm’s critique identified fundamental conceptual and methodological deficiencies in Kruse’s approach. Nahm demonstrated that Kruse’s claims about the immutability of F3 and F4 formants are not supported by voice forensics literature, that the methodology conflates different acoustic phenomena, and that alternative explanations (including sophisticated voice disguise techniques) were not adequately considered. Nahm concluded that Kruse’s approach, despite its technological sophistication, was “loaded with conceptual and methodological deficiencies that ultimately render his claims untenable.”⁴ This critique illustrates Nahm’s commitment to rigorous evaluation of investigative methods, regardless of their technological sophistication.

Evaluation and significance

Nahm’s work on physical mediumship occupies a distinctive position within parapsychology. He combines genuine openness to investigating reported phenomena (as evidenced by his sustained participation in the FEG circle) with uncompromising commitment to identifying fraud and methodological error. This dual stance reflects the central challenge in physical mediumship research: distinguishing between genuine anomalous phenomena and sophisticated deception.

His historical analyses demonstrate that physical mediumship has generated serious scholarly attention across multiple centuries and that interpretive frameworks for understanding mediumship developed more gradually and diversely than simplified narratives suggest. The recognition that early writers invoked human agency and psychic force explanations complicates any straightforward history of parapsychological ideas.

Nahm’s contemporary investigations reveal the persistent vulnerability of physical mediumship research to fraud. The FEG case demonstrates that even sustained, participatory observation by a trained investigator can fail to detect deception in real time, though careful analysis eventually reveals it. This finding has implications for evaluating historical cases where such detailed documentation and follow-up investigation were impossible.

His methodological critiques establish standards for evaluating technological approaches to mediumship investigation. The Kruse commentary shows that sophisticated instrumentation and signal processing do not automatically confer validity on conclusions; the underlying conceptual framework and assumptions about voice forensics must themselves be rigorously examined.

Collectively, Nahm’s contributions to physical mediumship research emphasize the necessity of combining historical scholarship, direct observation, technical expertise, and critical skepticism. His work suggests that while physical mediumship remains a legitimate research domain, claims of genuine phenomena require extraordinary evidence and must withstand rigorous methodological scrutiny. The persistence of fraud in contemporary circles, despite investigative oversight, underscores the difficulty of establishing authentic physical mediumship phenomena under controlled conditions.