It is true that we live in the 21st century but ghost stories are still one thing that seem to never depart from the personal recollections of people alleging their existence. Anecdotal experiences such as these, quite often, shade into age-old convictions that are kept alive by the tradition of spoken testimony.
But, what evidence is there indeed that ghosts or spirits for that matter do exist? Nothing but reported sightings that cannot be independently verified or confirmed. For some reason, they always have to be where we cannot find them which is not good evidence, if it is even evidence at all. Why do they have to hide themselves anyways? If something exists, it would be out there.
Purveyors of such superstitious jive always tend to rely on the famous aphorism that absence of evidence is not evidence of absence as proof. That is a logical fallacy because it requires that something must exist simply because we cannot prove that it does not. Indeed, absence of evidence should not even be a good reason to believe something.
The correct way to convey such a generalization is to say that absence of evidence is not always evidence of absence. But, it certainly can be. In particular, if there is positive evidence pointing to the prediction that we should not see said evidence and we indeed fail to, then that is indeed good evidence of absence.
By definition, ghosts are spiritual remnants of a deceased individual. They do not possess material presence but do possess some sort of conscious operation. To presume that they exist would mean to have to suspend the laws of thermodynamics. Energy cannot be created or destroyed, but it can only change from one form to another and matter and energy eventually disperse towards maximum disorder. Indeed, our biological systems are governed by these laws. Energy from the sun is used by enzymes to form high-energy bonds in our living cells. Cellular respiration uses chemical bond energy to do work and give off heat in the process. A continuous flow of energy maintains such systems. We are, accordingly, energy-processing devices that act to temporarily preserve order. Gradual loss of order ends with death. But, that is indeed what has to happen such that we can live in the first place.
The existence of ghosts would contravene the laws of thermodynamics as ghosts would need a source of energy and even then, energy would have to be added to maintain order and structure. Ghost believers try to circumvent that by presuming the existence of some sort of metaphysical emotional energy which again, like all sorts of occult pseudoscience, is designed such that it cannot be tested by laboratory experiments and empirical abstraction. Thus, we have no way of determining whether such a thing exists. Again, it has no observable consequences and cannot be tested. And, it is nonsensical because any form of energy, in accordance with the laws of thermodynamics, must eventually dissipate and thus would not allow for the persistence of ghosts which are thought to be immortal spirits. What’s the point of a ghost that dies anyways? The whole idea is largely an attempt to hijack physics and science so as to prove the existence of things for which science really has no real interest.
This also applies to any other manifestation of occult mysticism (spirits, fairies, demons, unicorns etc). It is quite ironic that proponents of such claims would use the inability of science to prove their existence as their evidence when at the same time they are really hijacking scientific concepts to explain what it is that they are saying. You could use their exact same arguments to purport the existence of Santa Claus, Mickey Mouse, and Winnie-the-Pooh. How else could one reach a definite conclusion with such ambiguous speculations? The evidence that ghosts exist is as equally weak as the evidence that Mickey Mouse exists. It is true we cannot prove that they don’t exist. But, we can, however, say that they almost certainly don’t exist.