Are ghosts always hallucinations? What is an hallucination? In the case of hallucinations, there is no defect in optics, the defect is in ocularity -- that is, the ocular vision is influenced by different thought-waves. These hallucinations may be of two types, positive and negative. In a positive hallucination, there is no physical defect in the ocular vision. Rather, one's vision is affected by the thought-waves which want to see something different.
And what is a negative hallucination? Here also there is no defect in the ocular vision, but due to excessive pressure of the thought-waves -- we say "auto-suggestion" -- the ocular vision becomes negative; that is, the thought-waves do not want to see something which is actually present in the ocular vision.
Many scholars are of the opinion that so-called ghosts are positive hallucinations, and sometimes people are also misguided by negative hallucinations. They say that in this case the ocular vision -- the optic nerves -- is deceiving them, but actually the main role here is played by the thought-waves, not by any physical organ, or psychic cells, or psycho-physical cells (ectoplasm).
It is said, Abhibha'van'a't citta'n'usrs't'apretadarshanam ["The sight of ghosts is created by the citta'n'u (mind-stuff) in concentrated thought"]. Abhibha'van'a means "cellular suggestion" -- that which affects not only the mind but also the nerve cells, so that due to the defective functioning of the nerve cells one sees something which is not present, or does not see something which is actually physically present. Cellular suggestion is of two types: auto-suggestion and outer-suggestion. Auto-suggestion takes place within the jurisdiction of one's own mind, in the individual mind, whereas outer-suggestion is the transmission of suggestion from another's mind, from another, stronger, mind. When a weaker mind is greatly influenced by a stronger mind, as a result something is not seen or nothing is seen.
You know, philosophically, whatever we see in this universe is, we may say, a positive hallucination created by the Supreme Consciousness (Parama Purus'a*). Whatever He thinks is seen by the nerve cells of the individual mind. The difference between this practical world and ghosts is that in the case of ghosts the suggestion comes from the individual mind; one's own thought is projected outside.
But when people see so-called ghosts and apparitions, are they always positive hallucinations? No, they are not. Whatever we observe in this physical world is made of the five fundamental factors (solid, liquid, luminous, aerial and ethereal), created in such a way that it automatically functions. Its inherent capacity for action is derived from this physical world under the inspiration of the Supreme Consciousness.
There may be some entities that do not require food and drink. Any entity composed of solid and liquid factors will certainly require food and drink, because food is mainly composed of the solid factor, and drink is mainly composed of the liquid factor. But if any entity is composed only of the other three factors -- luminous, aerial, and ethereal -- without any solid or liquid, then that entity is called a "luminous body".
By means of nerve cells, the mind operates the physical body: by creating vibrations such as smell, form, touch, taste, etc., the nerve cells either receive tanma'tras (inferential essences) or projects them externally. But luminous bodies have no nerves, because nerve cells and nerve fibres are all physical; thus they cannot function properly. Only, as in auto-suggestion, they may create a vibration within, and experience some type of feeling.
These luminous bodies are not ghosts or apparitions; they have nothing to do with them. Neither are they related to auto-suggestion or outer-suggestion. Under some circumstances, if someone happens to see this kind of luminous body, one may think one is seeing a ghost. But actually there is no ghost at all -- it is only a luminous body. It is not possible to see luminous bodies in broad daylight; it may be possible during the darkness of night, but then not everywhere.
It is said that there are seven kinds of luminous bodies: yaks'a, siddha, gandharva, kinnara, vidya'dhara, prakrtiliina and videhaliina. They are categorized according to their respective psychologies.
Suppose there is a very elevated person who often ideates on the Supreme Consciousness, but who has some greed for wealth. He or she does not, however, express it openly to the Supreme, nor does he or she even think of it directly. He or she thinks indirectly, "Oh, since I am a devotee of the Supreme Consciousness, He will certainly give me enormous wealth and make me immensely rich." Those who harbour this sort of covert desire are reborn as yaks'as. Thus sometimes we refer to "the wealth of the yaks'as".
The second is vidya'dhara. Those who have vanity of knowledge, although they do not expressly beseech this from the Supreme, but rather think inwardly that the Supreme should bestow an enormous wealth of knowledge upon them -- this type of person is reborn as vidya'dhara. Vidya'dhara is also a luminous body.
The next is gandharva. Those who have a great talent for higher music (people should cultivate music to the maximum to give pleasure to the Supreme Consciousness) and mentally think, "Oh, Parama Purus'a, I want knowledge of the science of music, not You" -- they are reborn as gandharvas. (In Sanskrit the science of music is called ga'ndharva vidya'.) They are also luminous bodies; they are not ghosts at all. They are also not visible in daylight, just as other luminous bodies are invisible.
The next is kinnara. Those who are vain about their physical beauty, or those who pray to the Supreme to give them more and more physical charm, are reborn as kinnaras. They are also luminous bodies.
Then siddha. Those human beings who are doing sa'dhana'**, who have great love for Parama Purus'a, but in their heart of hearts are proud of their occult powers or pray to Parama Purus'a to grant them still more occult powers -- these people after death are reborn as siddhas. Of all the categories of luminous bodies, the siddhas are the most elevated. They often help sa'dhakas in their sa'dhana'.
All these luminous bodies are collectively called devayoni. Besides the above, there are videhaliina and prakrtiliina. Those who wrongly worship Parama Purus'a in the form of clay, iron or other material substances, are ultimately transformed into prakrtiliina.
The next is videhaliina: those who run after occult powers and think, "I will attain such great occult power that with it, I will move from place to place." These are all luminous bodies; they are not ghosts, nor are they positive or negative hallucinations.
Thus ghosts are not positive hallucinations, or negative hallucinations, or siddhas or devayonis. Then is there any such things as ghosts? Not exactly ghosts, but there is something like that.
After death, when the mind dissociates from the body, the accumulation of unfulfilled sam'ska'ras*** or reactive momenta remains, although the body with the five fundamental factors no longer exists. Thus, the mind cannot function, but it remains in potential form. Now, in some circumstances, if the ectoplasm of a living person is associated with that disembodied potential mind, then that disembodied mind gets a mental body temporarily, for a very short time. Then that mental body can start functioning with the help of the nerve cells and nerve fibres of that living person, but only for a few minutes.
What is this called? It is neither a positive hallucination or a negative hallucination, nor is it a luminous body (devayoni). Then what is it? A living person's ectoplasmic cells become the mental body of a dead person for a few minutes until -- after a few minutes -- that mental body again dies. This mental body I will call pres'itama'nas -- "re-created mind."
Some people may do good works or get good works done with the help of these pres'itama'nas, but only those who have perfect control over their minds and over the nerve cells and nerve fibres of their bodies can do this.
Those who are bad people can do evil deeds with the help of these pres'itama'nas. They can hurl stones into others' houses, throw bones, or overturn tables and cots -- all these things can be done for only a few minutes.
So we see that what we call a "ghost" is not always a positive or a negative hallucination, nor is it always a siddha or a pres'itama'nas. In fact, we cannot prove the existence of a pres'itama'nas or siddha, and insofar as positive hallucination is concerned, it does not have any actual existence at all. If you see a positive hallucination, it is a mental disease.
If anything of this sort (pres'itama'nas or luminous body) comes before you, there is only one remedy to remove it: that is, do kiirtana or devotional chanting. Do kiirtana for one minute or repeat your guru mantra, and that "ghost" will instantly vanish into thin air. So under no circumstances should you be afraid.
Parama Purus'a* Universal Mind, Supreme Consciousness, the psyche and substance within which all things exist, with an emphasis towards subtlest realms of being, a threshold attainable by humans through sa'dhana'
sa'dhana'** Intuitional science carrying the practitioner progressively into subtler realms through appropriately designed processes positively affecting every realm of life and mind, and leading toward merger [yoga] back into Universal Consciousness.
sam'ska'ra*** The reactive momentum resulting from one's thoughts, words or deeds -- too often misnamed "karma", which is the proactive engagement in the manifest universe with ideation upon the whole of the universe and the centricity from which it generates, operates and into which each and every being returns from its individuation. The term "karma" is all too often misappropriatedly used when sam'ska'ra is the proper term. "Karma", properly used, means action performed with the ideation of the Supreme Consciousness at all times throughout an action. "Kriya", properly used, means performing action without cosmic ideation, and consequently racks up sam'ska'ras.