This dissertation follows American ghost hunters in their search for answers to questions of the afterlife and ultimate “truth.” It is an account of how they piece-meal disparate knowledges and paradigms—including traditional religions, New Age philosophies, and even popular understandings of science—to transform invisible and ephemeral ghosts into empirical objects of inquiry. In this dissertation, I trace paranormal research to a movement from within the scientific community. In the wake of Darwin’s theory of evolution, American psychologist and philosopher William James and a small group of distinguished scholars formed the American Society for Psychical Research to scientifically investigate exceptional mental states and more controversially, the possible postmortem survival of human consciousness. Fearing that the advance of science threatened to render the role of religion obsolete in modern society, James developed a theory of pragmatic truth, treating God and other supernatural beliefs as “real” insofar as they fulfilled personal needs and produced practical consequences. I engage with James’ psychical research and pragmatism to historically situate ghost hunting within longstanding theoretical debates on how to empirically study the supernatural and how to account for the endurance of spiritual beliefs amidst an increasingly “rational” technoscientific society. More precisely, I treat James’ pragmatism as both a historical milieu and an analytic to understand how ghost hunters conceive of and do the work of paranormal research within the legacy of early psychical researchers. Paranormal research is, and has always been, defined by uncertainty: nonstandard and competing theories, research protocols, and standards of evidence. When faced with this uncertainty, ghost hunters must often rely on “other” knowledges not recognized by the scientific method, such as gut feelings, hunches, and personal experiences, alongside positivist reasoning in order to track paranormal activity. By delving into the experimental world of ghost hunters, I use the popular idiom of the “paranormal” to speak more broadly to the ways in which we negotiate between rationality and irrationality, knowing and feeling, and belief and proof in our understandings of ourselves, our common experiences, and our social worlds.