As reported elsewhere, I was certain that these experiences were dreams or hallucinations for a long period in the early stages. They were seriously … - Robert Monroe

The experiences differ from the typical dream state principally in the following ways: (1) Continuity of some sort of conscious awareness; (2) Intellectual or emotional (or blends of the two) decisions made during the experiences; (3) Multivalued perception via sensory inputs or their equivalents; (4) Non-recurrence of identical patterns; and (5) Development of events in sequence that seem to indicate a time lapse.

According to the literature of the psychic underground, the religious-mystical history of man constantly makes reference to this Second Body. Long before Christianity and the Bible appeared, cultures in Egypt, India, and China, to name a few, held the Second Body idea as standard operating procedure. Historians have found these references again and again, but evidently consigned them to the mythology of the times.
If one reads the Bible from this point of view, the belief is confirmed many times in both the Old and New Testaments. In the Catholic Church are found consistent reports of saints and other religious figures having such experiences, some of them willfully. Even in Protestantism, devout followers have reported the out-of-body experience during some form of religious ecstasy.
In the Orient, the concept of a Second Body has long held a natural and accepted position of reality.

In the fall of 1964 an interesting meeting was held one evening in Los Angeles. It was composed of some twenty assorted psychiatrists, psychologists, scientists, et al—and myself. It was a most rewarding evening. The purpose of the meeting was to examine with sincerity and seriousness the experiences and experiments which have been condensed herein. After several hours of interrogation by the group, it was my turn. I asked two simple questions of each of them:
"If you were going through what I have been experiencing, what would you do?"...It was the definite opinion of the majority—more than two thirds—that every effort should be made to continue, such experimentation in the hope of enlightening and expanding man's knowledge of himself. Several half seriously stated that I should run, not walk, to the nearest psychiatrist. (None present offered his services.) The second question: "Would you, personally, take part in experiments that would lead to the creation of such unusual activity in yourself?"