A few years before his death in 1900, Henry Sidgwick, the founding president of the Society for Psychical Research, despairingly conceded that ‘we have not, and are never likely to have, empirical evidence of the existence of the individual after death’. For Sidgwick, as for his principal associates Edmund Gurney, Frederic Myers and Frank Podmore, the quest for proof of survival was in every sense a matter of life and death. All four suffered from bouts of crippling depression; both Gurney and Podmore almost certainly committed suicide. If there was no afterlife, Sidgwick declared, no prospect of reward or punishment beyond the grave, then this life would be meaningless; morality would have no foundation, and moral ‘Chaos’ would be at hand. A single, indisputable instance of communication from the dead would suffice, but after countless hours of observation in the séance rooms of England, no such proof had been found.

The subject of ghosts is still, as Roger Clarke observes in his lively and absorbing study, closely entangled with the question of survival, which is why it remains so divisive. Surveys suggest that around half the population believe in ghosts. But no amount of evidence will ever persuade the militant