Oneiromancy is a form of divination based upon dreams. It is a system of dream interpretation that uses dreams to predict the future. Dream divination was a common feature of Greek and Roman religion and literature of all genres.

Oneirocritic literature is the traditional literary format of dream interpretation. Artemidorus was a professional diviner and author known for the five volume Greek work Oneirocritica. According to Artemidorus, the material for his work was gathered from diviners during lengthy travels through Greece, Italy and Asia.

Artemidorus writes that dream interpretation is nothing other than the juxtaposition of similarities, but like other types of Greek divination, including astrology, celestial divination and pallomancy, Oneiromancy became exceedingly complex, with a given dream subject to a number of interpretations.

Dreams occur throughout the Bible as omens or messages from God. Jacob dreamed of a ladder to heaven and his son Joseph dreamed of his future success and interpreted the dreams of the Pharaoh of Egypt. The Magi are told in a dream to avoid Herod on their journey home, and Joseph, husband of Mary, was directed to flee to Egypt.

Deja vu is the experience of feeling sure that one has witnessed or experienced a new situation previously The experience is frequently attributed to a dream, although in some cases there is a sense that the experience happened in the past.

The experience of deja vu seems to be quite common among both adults and children. In formal studies 70% of people report having experienced it at least once. References to the experience of deja vu are also found in literature of the past, indicating it is not a new phenomenon. It has been extremely difficult to evoke the deja vu experience in laboratory settings, therefore making it a subject of few studies. Recently, researchers have found ways to recreate this sensation using hypnosis.

In recent years, deja vu has been subjected to serious psychological and neurophysiological research. Scientifically speaking, the most likely explanation of deja vu is not that it is an act of precognition or prophecy, but rather that it is an anomaly of memory. It is the impression that an experience is being recalled. This explanation is substantiated by the fact that the sense of recollection is strong in most cases, but that the circumstances of the experience, such as when, where and how the experience occurred, are quite uncertain.

Likewise, as time passes, subjects can exhibit a strong recollection of having the unsettling experience of deja vu itself, but little or no recollection of the specifics of the event or circumstances they are remembering when they had the deja vu experience. In particular, this may result from an overlap between the neurological systems responsible for short term memory, events which are perceived as being in the present, and those responsible for long term memory such as events which are perceived as being in the past.

In other words, the events would be stored into memory before the conscious part of the brain even received the information and processed it. This would explain why one is powerless when trying to twist the outcome of the event in order to create a paradox. The delay is only of a few milliseconds and already happened at the time the consciousness of the individual is experiencing it.

Another theory being explored is that of vision. As the theory suggests, one eye may record what is seen fractionally faster than the other, creating that sensation of strong recollection upon the same scene being viewed milliseconds later by the opposite eye. However, this theory fails to explain the phenomenon when other sensory inputs are involved, such as the auditive part, and especially the digital part.

For instance, if one experiences deja vu of someone slapping the fingers on his or her left hand, then the deja vu feeling is certainly not due to his or her right hand to be late on the left one. Also, persons with only one eye still report experiencing deja vu. The global phenomenon must therefore be narrowed down to the brain itself, where one hemisphere would be late compared to the other.

Early researchers tried to establish a link between deja vu and serious psychopathology such as schizophrenia, anxiety, and dissociative identity disorder, with hopes of finding the experience of some diagnostic value. However, there does not seem to be any special association between deja vu and schizophrenia or other psychiatric conditions. The strongest pathological association of deja vu is with temporal lobe epilepsy. This correlation has led some researchers to speculate that the experience of deja vu is possibly a neurological anomaly related to improper electrical discharge in the brain.

Some believe deja vu is the memory of dreams. Though the majority of dreams are never remembered, a dreaming person can display activity in the areas of the brain that process long term memory. It has been speculated that dreams read directly into long term memory, bypassing short term memory entirely. In this case, deja vu might be a memory of a forgotten dream with elements in common with the current waking experience. This may be similar to another phenomenon known as deja reve, or already dreamed. However, later studies on mice indicate that long term memories must be first established as short term memories.

Not only is the link to dreams as they pertain to deja vu the subject of scientific and psychological studies, it is also a subject of spiritual texts, as is found in the writings of the Bahai Faith with quotes like “Behold how the thing which thou hast seen in thy dream is, after a considerable lapse of time, fully realized.”

John Lennon suggests that a feeling of remembering occurs in a sense that he might realize that what he had dreamt is now a relevant present action that is taking place right here right now:

I was once sitting down in the kitchen noticing that my plate seemed well too familiar, it seemed as if my head motions were foreseen, and that every move would trigger a continuation to happen. I had many deja vu’s as a child but this was extraordinary, I knew from the bottom of my heart that I had dreamed this situation years ago, as a little boy, that amazingly an entire piece of memory was regained and I finally understood when and where I was dreaming and how long this dream was, and most importantly how many years ago did I dream.

Those believing in reincarnation theorize that deja vu is caused by fragments of past life memories being jarred to the surface of the mind by familiar surroundings or people. Others theorize that the phenomenon is caused by astral projection, or out of body experiences, where it is possible that individuals have visited places while in their astral bodies during sleep. The sensation may also be interpreted as connected to the fulfillment of a condition as seen or felt in a premonition. 

The term deja vu was coined by a French psychic researcher Emile Boirac in his book The Future of Psychic Sciences, which expanded upon an essay he wrote while an undergraduate. The experience of deja vu is usually accompanied by a compelling sense of familiarity, and also a sense of strangeness or weirdness.

Precognition is a form of extrasensory perception where in a person is said to perceive information about places or events before they happen. A related term, presentiment, refers to information about future events which is said to be perceived as emotions. These terms are considered by some to be special cases of the more general term clairvoyance.

J. W. Dunne, a British aeronautics engineer, undertook the first systematic study of precognition in the early twentieth century. In 1927, he published the classic An Experiment with Time, which contained his findings and theories. Dunne’s study was based on his own precognitive dreams, which involved both trivial incidents in his own life and major news events appearing in the press the day after the dream. 

When first realizing that he was seeing the future in his dreams, Dunne worried that he was a freak. His worries soon eased when he discovered that precognitive dreams are common. He concluded that many people have them without realizing it, perhaps because they do not recall the details or fail to properly interpret the dream symbols. 

Joseph Banks Rhine and Louisa Rhine began the next significant systematic research of precognition in the 1930s at the Parapsychology Laboratory at Duke University. Rhine used card-guessing experiments in which the participant was asked to record his guess of the order of a card deck before the deck was shuffled.

London psychiatrist J. A. Barker established the British Premonitions Bureau in 1967, which collected precognitive data in order to provide an early warning system of impending disasters. Barker succeeded in finding a number of subjects who tuned in regularly to disasters, but were unable to accurately pinpoint the times. 

The Princeton Engineering Anomalies Research Lab is one of the more recent examples of attempts to study precognition, beginning in 1979, with precognitive experiments conducted in a variety of formats by various parapsychologists. This facility was closed in 2007.

An issue related to precognitive events includes paradoxes due to causality. One form of paradox includes events that are prevented due to the actions of those that know of it through precognition. In this case, the event doesn’t happen, which would prevent the viewer from seeing the event in the first place.

A subtler form of paradox is the circular cause and consequence problem of events that are actually caused by the foreseeing of the event. Though in and of itself this chain is logically consistent, it is a chicken or egg problemFor instance, if the event did not happen the viewer would not have seen it, which would have prevented it from happening.

Those skeptical of the existence of precognition and other forms of ESP believe it to be the result of self delusion and contend that selection bias is the cause of the belief that one has precognition where individuals remember the significant events and forget about everything else. Skeptics contend that the human memory naturally has a tendency to remember coincidences more often than other noncoincidences and thus individuals tend to remember more frequently when they were correct about a future event and forget the instances when they were wrong.