This is a big philosophical question and there are many answers available – but which one is more plausible then the others?
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There are many studies on young children that prove the existence of some prenatal knowledge, some forms of psychological patterns that are unexplainable except some special mechanism of conveying them exists.
The concept of psychological archetypes was advanced by the Swiss psychiatrist Carl Jung, c. 1919. In Jung's psychological framework archetypes are innate, universal prototypes for ideas and may be used to interpret observations. A group of memories and interpretations associated with an archetype is a complex, e.g. a mother complex associated with the mother archetype. Jung treated the archetypes as psychological organs, analogous to physical ones in that both are morphological constructs that arose through evolution.
Source: http://en.wikipedia.org/wiki/Archetype
According to Jung archetypes were part of the collective unconscious and these models are innate, universal and hereditary. They are not thought and act to organize how we experience certain things.
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An American psychologist called Michael Newton had published a book revealing all of his findings during 30 years of patients’ studies based on his regressive hypnotherapy looking back into their past-lives memories.
What’s interesting about most of these cases is that they tend to tell a similar story of the afterlife describing the realm that we live in between our lives. His book gives reasonable explanation as to why do we meet some people more often in our life, what is spiritual evolution and how the spiritual world is really designed.
Source: http://en.wikipedia.org/wiki/Michael_Newton_(hypnotist)
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There is another important work done by a Canadian biochemist and professor of psychiatry called Ian Stevenson. He devoted most of his scientific career to the research and proving of the past-life concept:
Stevenson considered that the concept of reincarnation might supplement those of heredity and environment in helping modern medicine to understand aspects of human behavior and development. He traveled extensively over a period of 40 years to investigate 3,000 childhood cases that suggested to him the possibility of past lives. Stevenson saw reincarnation as the survival of the personality after death, although he never suggested a physical process by which a personality might survive death.
Source: http://en.wikipedia.org/wiki/Ian_Stevenson
Ian Stevenson published many books describing amazing stories of 3-5 year old children with many of them unambiguously making a meaningful link between a previous life of one person and the new one of this child.
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Considering all of these research works we should keep in mind that in our world there are still many unexplained phenomena that tend to mystify our scientists even today – some of them called ESP phenomena:
Extrasensory perception (ESP) involves reception of information not gained through the recognized physical senses but sensed with the mind. The term was coined by Sir Richard Burton, and adopted by Duke University psychologist J. B. Rhine to denote psychic abilities such as telepathy and clairvoyance, and their trans-temporal operation as precognition or retrocognition. ESP is also sometimes casually referred to as a sixth sense, gut instinct or hunch, which are historical English idioms. The term implies acquisition of information by means external to the basic limiting assumptions of science, such as that organisms can only receive information from the past to the present.
Source: http://en.wikipedia.org/wiki/Extrasensory_perception
All of those aspects are indicative of one level in our world that is present but not always consciously perceptible or observable – yet manifesting itself to our human senses – most enigmatic of which - the 6th sense
