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 into a room and documents an EM field, strange thermal readings, a garbled voice recording, etc. Further, let’s say that this was in an isolated area and somehow the “researcher” had accounted for all known sources of energy. Would he have just succeeded at proving the existence of the supernatural? NO! Because he document physical readings. All that he would have shown was that something happened that we don’t currently understand. You cannot jump from “we don’t understand X” to “X is caused by ghosts.” That’s a logical fallacy known as an argument from ignorance.

This is the hilarious paradox that entertains me to no end: if supernatural ghosts exist, then they are, by definition, untestable using science. Thus, using scientific equipment to look for ghosts is inherently self defeating!

We basically have three possibilities:

Ghosts don’t exist Supernatural ghosts do exist, but cannot be tested using science “Ghosts” exist, but are a actually natural, physical phenomena, in which case they can be documented using science

There is no option 4 in which supernatural ghosts exist and can be documented using physical means. That’s just not possible. If ghosts are supernatural, then their existence cannot be demonstrated using science, and conversely, if their existence can be demonstrated using science, then they aren’t supernatural. If you document an unexplained physical clue, then all that you can say is, “we don’t understand this.” You cannot assume that the physical clue was caused by the metaphysical. Indeed, if you think through the history of science, there have been numerous physical phenomena that were attributed to the supernatural before we properly understood them.

Additionally, there is the paradoxical nature of ghosts hunter’s equipment. The equipment that they use to “detect” ghosts is generally designed by them and is based on question begging fallacies. For example, ghost hunters generally argue that ghosts put off an EM field which their equipment can detect, and we can set up their argument like this:

Ghosts emit an EM field I can detect a ghost’s EM field using this device I built I went into an abandoned house and detected an EM field Therefore, a ghost was present

The problem is premises 1 and 2. I would not accept that ghosts put off a detectable EM field unless I was already convinced that ghosts exist. In other words, before you can use an EM field as evidence of a ghost, you have to demonstrate that ghosts put off EM fields, but you can’t demonstrate that ghosts put off EM fields, unless have already demonstrated that ghosts exist! Round and round in a circle we go.

In short, ghost hunting is inherently self defeating because it starts by assuming that ghosts exist and because no amount of physical evidence can ever demonstrate the existence of the metaphysical. To demonstrate the existence of the metaphysical, you would need metaphysical evidence, which science cannot supply for you. So if you want to believe in the supernatural, you are going to have to do exactly that: believe. You cannot, even in concept, support your belief with physical evidence.