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Ghost themed shows and ghost tours in some cities probably make ghost-related entertainment products a multi-million dollar industry.

A ghost is supposedly the spirit of a deceased person who rises again as a translucent spirit that causes mischief or re-enacts some moment from its life.

The problem is that I have never witnessed a ghost in my everyday life. Therefore I wonder is there any scientific data at all that would support the existence of ghosts or similar spirits?

Or is the concept of ghosts merely exploiting the superstitions of the average human so that some people can make money and provide entertainment?

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locked by Sklivvz May 5 at 17:54

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Related questions about photos of ghosts: skeptics.stackexchange.com/questions/421/… –  Fabian Mar 13 '11 at 8:16
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Sorry, I have to: xkcd.com/1235 –  Jens Aug 15 '13 at 6:36

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up vote 42 down vote accepted

According to Wikipedia, and common understanding1, the definition of a ghost is the following:

In traditional belief, a ghost is the soul or spirit of a deceased person or animal that can appear, in visible form or other manifestation, to the living.

As such, before we can scientifically investigate such a phenomenon, we need to understand what the soul is. Without a working definition of soul, it is not clear how we could discern natural manifestations from real ghosts.

Now, the soul is the transcendant part of a human being, in other words it can be described as what is left of a person if you take away the body.

Soul, in religion and philosophy, the immaterial aspect or essence of a human being, that which confers individuality and humanity, often considered to be synonymous with the mind or the self.
-- source

Practically speaking, there has to be a soul for ghosts to exist at all, and the soul must be separable from the body, through death.

Belief in ghosts is based on the ancient notion that a human spirit is separable from the body and may maintain its existence after the body’s death.
-- source

Now - what problems do the previous definitions pose to scientific research?

First of all, any working definition of the soul is strictly unscientific: the soul is intended to be non-corporeal (or in other words, pretty much unmeasurable). So we are left with little or no means of substantiating a claim on ghosts - they can only be believed in, but not studied via physical detection.

Secondly, as any soft, non-scientific concept, it is nearly impossible to define: on the wikipedia page there are no less than 22 different religious definitions of the soul.

Lastly, all our scientific investigation on the workings of the mind through neuroscience has been quite effective in discovering many examples of parts of our consciousness which are physical in origin and not due a separate soul-like entity.

Therefore, it is completely impossible to determine via experiment if ghosts exist. We don't know what they should be, how and if we should be able to measure them, and there are some strong indications that they would be very different from what common definitions would make them.

As a skeptic, this should make your alarm bells start ringing like crazy! We are clearly in a Russell's teapot situation where something is so vague that it is impossible to disprove, however it is clear that it is scientific nonsense.

The best we can do is to debunk specific claims of ghost appearances.


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Can it not be said that since, by definition, there is no interaction between the corporeal and the transcendent non-corporeal, there is no manner in which ghosts exist "in the world"? Consciousness and free will are problematic enough to philosophers, but at least most agree that consciousness is associated with a physical living brain. Take away that physical structure, and you have nothing on which to hang an "exists." –  Larry OBrien Oct 11 '11 at 18:23
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@Sklivvz A teapot is a teapot there is no such thing as a giant teapot that a human can use. It is clear he refers to a normal sized teapot. "A satellite in orbit" it is pretty evident where it is --> in orbit. You don't need a specific place. I am in germany, if I don't specify the city it doesn't make it vague. And it already says a specific place in orbit --> between mars and earth. –  Joze Oct 12 '11 at 11:08
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@Oddthinking: Incorrect, according to the proponents, ghosts are material, e.g. you can see them. The problem is that every time you try an experiment, they do not appear. In the same way, asserting there is a teapot between here and Mars does not guarantee at all that we can find it with an experiment. The proof the assertion is vague is that proponents can always say "the experiment is correct, but you looked for the teapot/ghost in the wrong place". –  Sklivvz Oct 12 '11 at 12:08
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@Sklivvz, I concede all your facts without checking them. We are effectively arguing about what the term "vague" means, and how one measures it. You are arguing the large volume makes the teapot claim quantitatively vague. I am arguing that the fact that it (ignoring its unknown origin story) is consistent with all the known laws of physics makes it qualitative less vague than the concept of a material aspect of an immaterial aspect of one species of animal - only subject to some laws of physics sometimes (e.g. gravity - what stops it flying off into space?) –  Oddthinking Oct 12 '11 at 13:51
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An aside: Is it useful to equate non-corporeal with unmeasurable? Would energy be considered non-corporeal? Might anything outside the physical human body be considered non-corporeal? In that sense, I am not sure the equating is useful or correct, since we regularly acknowledge both energy and physical non-corporeal entities. Perhaps that is why so many "ghost hunters" are apt to use language that includes words such as "frequencies" and "spectrum" - drawing analogy to radio. The trick seems to be that a ghost is at the same time non-corporeal and human (or humanoidish/sentient/demonic/etc). –  Brian M. Hunt Aug 15 '13 at 1:37

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