Source: The Logic of Science
Many people believe in the paranormal, and a great deal of time and effort is spent searching for evidence of it. Indeed, shows like “Ghost Hunters” are extremely popular, and the notion of using scientific equipment to detect the supernatural is well ingrained into our literature, movies, and culture more generally. The reality is, however, the ghost hunting is a perfect case study in pseudoscience, and it is based on a series of logical fallacies and amusing paradoxes.
Most obviously, ghost hunting (along with related pseudoscientific ventures such as UFO spotting, searches for Big Foot and Nessy, Creation Research, etc.) suffers a serious flaw which automatically removes it from the realm of science. Namely, it starts with a conclusion (i.e., ghosts exist), then tries to prove that conclusion. In contrast, real science always starts with the evidence, then forms a conclusion based on that evidence. This distinction is extremely important, because if you start with a conclusion, you will inevitably find a way to twist the evidence to fit your preconceived view, even if it results in ad hoc fallacies. For example, suppose that ghost hunters go into an abandoned building and detect electromagnetic energy (EM). They will view that as evidence of a supernatural presence, but to those of us who aren’t already convinced that ghosts exist, that energy could be a bad wire, a faulty transformer outside, the cameras, lights,and other equipment being used by the ghost hunters, etc. You see, the explanation that the energy is coming from a ghost is only convincing if you are already convinced that ghosts exist. This is why real science always has to start with the evidence, then form a conclusion. If you set out to prove something, you will always find a way to do it (at least in your mind).
Ghost hunting also suffers a serious paradox which is somewhat unique to it, and which I find highly entertaining. Ghosts are supposed to be paranormal, supernatural, metaphysical, etc. yet ghost hunters try to document their existence by looking for physical clues. This is problematic because, by definition, science is the study of the physical universe. It is inherently incapable of answering questions about the supernatural. So anytime that you are looking for the metaphysical, you are automatically doing pseudoscience, not science.
To put this another way, you cannot prove the existence of the metaphysical by documenting the physical. Let’s say, for example, that a ghost hunter goes . . .