164 THE FEMALE THERMOMETER these works was the same: spectres were products of the imagination Yet herein lay an unforeseen epistemological pitfall The paradoxical effect of the psychological argument was to subvert the boundary between ghost-seeing and ordinary thought Of course some apparitions could be attributed, quite simply, to specific pathological causes—fevers, head injuries, inhaling or imbibing stimulants But the rationalists, at the same time, could not forebear reaching after a seemingly more universal or totalizing explanation: that thought itself was a spectral process, and, as such, easily modulated into hallucination Ferriar led the way by confusing the distinction between simple recollection and the "faculty of spectral representation." "From recalling images by an art of memory," he wrote, "the transition is direct to beholding spectral objects, which have been floating in the imagination."55 But others soon enlarged on the spectral nature of contemplation It was possible for the mind to become so absorbed by an idea, wrote William Newnham, that the idea "then haunts its waking and its sleeping moments."56 "The objects of mental contemplation," Samuel Hibbert observed, "may be seen as distinctly as external objects."57 Describing "Ghosts of the Mind's Eye, or Phantasma" in his philosophical dialogue The Philosophy of Mystery, Walter Cooper Dendy, senior surgeon at the Royal Infirmary for Children, concluded that a ghost was "nothing more than an intense idea" and that seeing a phantom was "an act of thinking." Yet if ghosts were thoughts, it was not far to go, through a kind of symbolic recoil, to a perception that thoughts were ghosts: It is as easy to believe the power of mind in conjuring up a spectre as in entertaining a simple thought; it is not strange that this thought may appear embodied, especially if the external senses be shut: if we think of a distant friend, we not see a form in our mind's eye, and if this idea be intensely defined, does it not become a phantom? Between an idea and a phantom, wrote Dendy, "there is only a difference in degree; their essence is the same as between the simple and transient thought of a child, and the intense and beautiful ideas of a Shakespeare, a Milton, or a Dante."58 In the end, it seemed, one could no longer distinguish between the specialized psychic act of seeing a ghost and the everyday business of remembering or imagining Brierre de Boismont made this indeterminacy strikingly obvious when he argued for the existence of what he called "normal hallucinations"—the "delirious conceptions forever flitting around man, similar to those insects that are seen whirling around by thousands on a fine summer evening" (HD, 354, 359) 59 And in a crucial passage on the etiology of illusion, he found an even more suggestive metaphor: Sufficient attention has not been bestowed on this misty phantasmagoria in which we live Those undecided forms, which approach and retire unceasingly, with a thousand tantalizing smiles, and after which we run with so much ardor, travel through our brains, emerge from their clouds, and become clearer and clearer; then the