Chapter Three analyses the ‘theoretical’ connections that many physical-psychical scientists made between ‘physics and psychics’. It analyses general physical arguments against philosophical materialism and other ‘stumbling blocks’ to the idea of mind and spirit in the cosmos; vague analogies between physical and psychical effects; and more radical physical theories and explanations of telepathy and other psychical phenomena. The chapter highlights the extrordinary creativity of physical scientists in applying their concepts, ideas and theories to psychical puzzles. It also examines the criticism that many physicsts levelled against such psychical uses of physics and argues that while leading physical-psychical scientists accepted many of the problems with physical theories of largely non-physical phenomena, they never completely abandoned the idea that some kind of physical theory would ultimately help render psychical effects more intelligible.

Chapter Six examines the trajectory of physical-psychical scientists in the early twentieth century. By 1900 the network of physical-psychical scientists was weaker because many had died or were too old or busy to commitment themselves to new experimental enquiries. Those strongly committed to psychical research tended to explore connections between physics and psychics via writing rather than new experiments. The writing of Lodge, Barrett, Kingsland and others explored the connections between psychical research and modern developments in physics and religion. Many thought that Lodge’s connections went too far while others did not think the connections went far enough. Among those who sought to transcend Lodge were professional and amateur radio enthusiasts, and psychical researchers, and a younger generation of psychical researchers who believed relativity and quantum theories was more effective than older, mainly ether-based physics, at rendering psychical effects plausible.

The conclusion examines the legacy of physical-psychical scientists. By the 1940s even the most sympathetic physical-psychical scientists were ambivalent at best about the ‘psychical’ achievements of Crookes, Lodge and other veteran physical-psychical scientists. From the 1940s until the 1960s very few of the connections between physics and psychics involved the modern physics of relativity and quantum theories; the 1970s, however, saw a rejuvenation of interest in these possibilities, which became a major focus of the new field of ‘paraphysics’ whose theories and practices continue to cause controversy. I argue that the protagonists of this book would have recognised many of the problems faced by practitioners of paraphysics but repudiated these practitioners’ perceptions that Victorian physics was materialistic, rigid and closed to psychical significance.

Chapter Two surveys what we call ‘physical-psychical scientists’ - physical scientists who, from the early nineteenth to the early twentieth century, showed some kind of interest in psychical phenomena. It uses the membership of Society for Psychical Research to identify many such physical-psychical scientists. Analysing this membership, and individuals who expressed their psychical interests outside the organisation, the chapter argues that these interests were far more extensive and complex than historians have argued. The chapter analyses the ways in which this collective interest was facilitated by existing institutional and other connections. It explores the range of intellectual, religious, moral and emotional reasons that underpinned this interest, the different positions and conclusions that different scientists reached after their investigations, and the reaons why so many scientists abandoned their interest in such studies or were actively hostile to them.

Chapter Four focuses on the experimental approaches of physical-psychical scientists to psychical phenomena. It focuses on four key examples from the 1870s-1890s: William Crookes’s investigations of ‘psychic force’ ; Crookes and Cromwell Varley’s electrical tests of mediumship; the SPR’s studies of Reichenbach’s ‘od’ ; and Oliver Lodge and Benjamin Davies’s ideas about and experimental tests of telekinesis. The chapter shows the extraordinary lengths to which physical-psychical scientists went to achieve greater control over, to measure and record psychical effects, and to turn domestic seances into sites of experimental physics. The limited effectiveness of this work was partly due to perceived flaws in experimental design, a lack of suitable experimental subjects (mediums), and because physical-psychical scientists believed their professional and intellectual goals were better served by focusing experimental research on purely physical topics.

Chapter Five examines the problematic nature of expertise in psychical investigation, and the equally troublesome question of whether skills in the physical sciences were relevant to and useful in such investigations. Although spiritualists, psychologists and conjurors disagreed about many other psychical-related issues, all three kinds of audience shared grave misgivings about physical scientists in sites of psychical enquiry. This chapter argues that while psychologists sought to exclude physicists from psychical enquiry because they perceived huge differences between ‘tricky’ psychical instruments and reliable instruments of physics, leading physical-psychical scientists sought to collapse this distinction: they often believed that their experience of and skills in handling ‘tricky’ instruments of physics gave them important qualities to bring to the psychical expert.

Chapter One explores ancestors of the idea that the physical sciences were relevant and significant to the study of obscure powers associated with the human body and mind. In the late eighteenth and early nineteenth centuries, practitioners of animal magnetism and mesmerism linked the study of a supposed new imponderable ‘magnetic’ fluid affecting health to better-known physical imponderables. In the mid-nineteenth century the German chemist Karl von Reichenbach and his followers stimulated much debate for their alleged discovery of new imponderable ‘od’ that they believed extended the domain of physics into the realm of physiology. From the 1840s onwards ’Modern Spiritualism’ prompted many natural philosophers to intervene on controversies over its startling physical effects. The final section of the chapter contextualises these attempts to link physical and psychical realms in terms of the fluid state of the physical sciences in the early and mid-nineteenth century.

The introduction sets out the historiographical framework and principle approaches of the book. Studies of nineteenth and twentieth century interactions between the established sciences and psychical phenomena have yielded many important insights but left many questions unanswered. We know a good deal about the psychical interests and investigations of a handful of scientists but only a partial sense of how far their examples were followed. We know a lot about the ‘occult’ uses to which spiritualists, theosophists and other occultists put developments in physical sciences relating to ether, energy, electricity and matter, but far less about the uses to which scientists made of psychical and occult phenomena in their scientific enquiries. Existing studies have also established much about the connections between ’physics and psychics’ at the level of ideas, theories and concepts, but have largely sidestepped the experimental nature of these connections.