"In the ages of the rude beginning of culture," wrote Nietzsche, "man believed that he was discovering a second real world in dream, and here is the origin of all metaphysics. Without dreams, mankind would never have had occasion to invent such a division of the world. The parting of soul and body goes also with this way of interpreting dreams; likewise, the idea of a soul's apparitional body: whence all belief in ghosts, and apparently, too, in gods." 
I am inclined to agree with Nietzsche in placing the blame for belief in ghosts, gods, and life after death on the doorstep of the dream. Let us suppose that the idea of a soul-body derives from subjective experiences in the dream world. Whether or not the soul would then be granted the status of objective reality would depend on the reality status given to the dream.
If early humans believed they had discovered in the dream a second "real world," what might they have meant? Did they merely mean that the dream world had a subjectively verifiable existence? That dreams were only real while they lasted? Or did dreams exist actually and objectively in some subtle plane of existence every bit as real as the physical world?
These are only a few of the possibilities we might consider in trying to settle the question of whether dreams are real, and if so, how the mental reality of the dream world might compare with the physical reality of the world you are reading this book in.
There are really two issues here: one is the degree to which an experience seems subjectively real (at least while it is happening). The other issue is independent of the first; this is the degree to which the experience seems objectively real in the sense that it produces actual effects on other parts of reality. We say that something really exists if it can produce an effect (of any kind) on another member of some class of existence. As an example, imagine a very special little object, which is so soft that you can't touch it; and covered with invisible paint so you can't see it, and moreover transparent to every kind of light; it is also odorless; it has no weight; and it has no other property whereby it can be grasped. In short, there seems to be no way in which you can interact with it. So how would you know it exists? We only know a thing exists when it interacts with other existing things.
Now we come to the specific question that is relevant here: what about the reality of the dream? Our studies in Chapter 4 have shown without any doubt that lucid dreams produce real effects on our brains and bodies. Score one for the dream! There seems no doubt that dreams are as real as real can be, according to the subjective point of view of the dream.
But even though we have demonstrated the subjective reality of dreams, we have not faced the bigger question: is there any evidence suggesting that dreams can be objectively real as well? There are in fact several enigmatic phenomena that seem to raise the possibility that, in some circumstances at least, the dream world may be at least partially objective. One of these enigmas is the uncanny experience in which a person feels that he or she has somehow temporarily detached from or "left his or her body." Survey data indicate that a surprising number of people have had such so-called "out-of- body experiences" (OBEs) at least once in their lives.  Very frequently those who have this experience become unshakable convinced that they, or at least some part of themselves, are capable of existence independent of their bodies.
Another phenomenon whose existence is widely attested to is the mysterious mode of information transfer called extra- sensory perception (ESP). A wealth of anecdotal evidence supports the idea that ESP, working across both space and time sometimes occurs. If it is indeed possible to "perceive" in some fashion events that are happening at a distance, or even those that have not yet happened, space and time must be other than what they seem, and the same thing goes for subjective and objective!
Accounts of "mutual dreaming," (dreams apparently shared by two or more people) raise the possibility that the dream world may be in some cases just as objectively real as the physical world. This is because the primary criterion of " objectivity" is that an experience is shared by more than one person, which is supposedly true of mutual dreams. In that case, what would happen to the traditional dichotomy between dreams and reality?
These mysterious phenomena that threaten the simplicity of our common sense view of life are all primarily children of the night. Surveys indicate that more spontaneous psi experiences are reported to occur during dreaming than in the waking state.  Most out-of-body experiences tend likewise to occur while the person is dreaming or at least in bed. Dean Shiels, an American anthropologist, studied the OBE in 67 different cultures around the world and found that sleep was regarded as the most important source of OBEs in about 80% of the cultures in his sample. 
How does all this relate to lucid dreams? I propose that OBEs are actually variant interpretations of lucid dreams; that dream telepathy will provide the basis for an explanation of the occasional accuracy of paranormal OBE vision; and laboratory experiments with mutual lucid dreams will be suggested as a means of testing the objective reality of shared dream worlds.
Although telepathic experiences also apparently occur during the waking state, as I already mentioned, surveys indicate that most instances of such phenomena occur in precognitive dreams. The following is a remarkable example of such a dream.
" Many years ago when my son, who is now a man with a baby a year old, was a boy I had a dream early one morning. I thought the children and I had gone camping with some friends. We were camped in such a pretty little glade on the shores of the sound between two hills. It was wooded, and our tents were under the trees. I looked around and thought what a lovely spot it was.
I thought I had some washing to do for the baby, so I went to the creek where it broadened out a little. There was a nice clean gravel spot, so I put the baby and the clothes down. I noticed I had forgotten the soap so I started back to the tent. The baby stood near the creek throwing handfuls of pebbles into the water. I got my soap and came back, and my baby was lying face down in the water. I pulled him out but he was dead. I awakened then, sobbing and crying. What a wave of joy went over me when I realized that I was safe in bed and that he was alive. I thought about it and worried for a few days, but nothing happened and I forgot about it. During that summer some friends asked the children and me to go camping with them. We cruised along the sound until we found a good place for a camp near fresh water. The lovely little glade between the hills had a small creek and big trees to pitch our tents under. While sitting on the beach with one of the other women, watching the children play, I happened to think I had some washing to do, so I took the baby and went to the tent for the clothes. When I got back to the creek I put down the baby and the clothes, and then I noticed that I had forgotten the soap. I started back for it, and as I did so, the baby picked up a handful of pebbles and threw them in the water. Instantly my dream flashed into my mind. It was like a moving picture. He stood just as he had in my dream--white dress, yellow curls, shining sun. For a moment I almost collapsed. Then I caught him up and went back to the beach and my friends. When I composed myself, I told them about it. They just laughed and I said I imagined it. That is such a simple answer when one cannot give a good explanation." 
Anecdotes, though dramatic and numerous, do no more than convince one that precognitive dreams are a possibility. It takes scientific investigation to convert possibility to probability approaching certainty. Fortunately, there are perhaps half a dozen scientific demonstrations of dream telepathy.
The most famous among these were the experiments in dream telepathy carried out in the Dream Laboratory of the Maimonides Hospital in Brooklyn by Dr. Montague Ullman and Dr. Stanley Krippner in the late 1960s. These dream researchers monitored sleeping subjects. During the periods that the subjects were in REM sleep, a person in another room focused on an art reproduction and attempted to telepathically transmit an image of the painting to the sleeping subjects, who were awakened for dream reports at the end of each of their REM periods. Afterwards, judges were able to match which picture went with which dream report with an accuracy significantly above chance.
One night the target picture was The Sacrament of the Last Supper by Salvador Dali. The painting shows Christ at the center of a table surrounded by the twelve disciples, with a glass of wine and a loaf of bread on the table, and a fishing boat visible in the distance on the sea behind them. Dr. William Erwin was the subject. His first dream was about an ocean which he commented had a "strange beauty about it..." Remembering his second dream, he said, "boats come to mind. Fishing boats. Small-size boats...There was a picture in the Sea Fare Restaurant that came to mind...It shows, oh, I'd say about a dozen or so men pulling a fishing boat ashore right after having returned from a catch." Erwin's third dream seemed to relate to the Christian theme: he was looking through a "Christmas catalogue." His following three dreams were about doctors (Christ the healer and spiritual physician?) His last two dreams of the night dealt with food. In the morning Dr. Erwin's reflections on his dreams put the pieces together in a way that is very suggestive: "The fisherman dream makes me think of the Mediterranean area, perhaps even some sort of Biblical time. Right now my associations are of the fish and the loaf, or even the feeding of the multitudes....Once again I think of Christmas...Having to do with the ocean-water, something in this area..." 
The findings of the Maimonides program of research offer scientific support for the possibility of telepathic influence on dream content.  Likewise, in 1962, L. E. Rhine concluded on the basis of a large body of anecdotal evidence that more spontaneous psi-experiences occurred during dreaming than during the waking state. That being so, we may accept dream telepathy as a working hypothesis and are free to make explanatory use of it, if the need arises--which it shortly will.
But now let us return to the other enigma we were discussing: the out-of-body experience. The OBE takes on a confusingly wide variety of forms. A person having an OBE may for example find his sense of identity apparently associated with a second, non-physical body--a "soul," "astral body," "spirit," or, to suggest a term having a certain charm, "out-of-body body" (OBB)! Equally, while "out-of-body", one may entirely dispense with the inelegance of bodies of any sort, and experience oneself as a point of light or a freely mobile center of awareness. In some OBEs, one will seem to see one's physical body while in other cases one finds but an empty bed or someone else entirely.
Let us take the case of one "astral projector" who wrote that before he knew what his OBEs were, he "was much afraid each time" he had one. He explained that his projections always began with him lying in bed, feeling a weight holding him down. The next thing he knew he would be out of his body. During one OBE, he walked around his bedroom and looked down the stairs into the kitchen. He decided to look at himself in the mirror, but curiously could not see anything when he did so. On another occasion, when returning from "astral adventures," he thought, "I'll look at myself on the bed." But when he looked, he saw his mother, who "had been passed over quite a long time." Yet curiously, finding his dead mother in bed instead of his sleeping body didn't lead him to the conclusion that he was dreaming; he took this to mean that his mother's spirit would always be with him whenever he was "projected." 
Two features of this OBE report are particularly suggestive. One is that upon "leaving his body" the astral projector walked around "his bedroom" and looked into "the kitchen." This added to the second fact that he expected to find his own sleeping body in bed upon his return, indicates that he conceived of himself as being in a non-physical ("astral") body, but in an environment identical to the physical world. It is exactly this kind of contradictory and confused mixture of mental and material elements that is also characteristic of the pre-lucid or naive dreamer. Secondly, note the projector's failure to consider the possibility that if his physical body wasn't in the bed he was looking in, it might not be the real bed he was looking at, or the real bedroom, or the real kitchen, either.
These kinds of minor lapses of rationality and the failure to question the anomalies that confront one seem to me quite characteristic of non-lucid dreaming and OBEs. Here is an account by Keith Harary, a person who has impressed me in the waking state as quite rational and of superior intelligence, and who is, as well, unusually proficient at inducing OBEs:
" One night I awoke in an out-of-body state floating just above my physical body which lay below me on the bed. A candle had been left burning on [sic] the other end of the room during the evening. I dove for the candle head first from a sitting position and gently floated down toward it with the intention of blowing out the flame to conserve wax. I put my "face" up close to the candle and had some difficulty in putting out the flame. I had to blow on it several times before it finally seemed to extinguish. I turned around, saw my body lying on the bed and gently floated back and back into it. Once in the physical (body) I immediately turned over and went back to sleep. The next morning I awoke and found that the candle had completely burned down. It seemed as if my out-of-the-body efforts had affected only a non-physical candle." 
The fact that Harary considered the other objects as physical, and the candle alone to have been non-physical is very similar to the way that normal dreamers account for anomalies when they occur during a dream.
Harary claimed that this experience, like his other OBEs, was " subjectively distinguishable from dreaming in much the same way that waking consciousness is distinguishable from dreaming or imagination." This is exactly how lucid dreams are distinguished from ordinary dreams.
In addition to the anomalies that people tend to accept in OBEs, there is another similarity to dreaming. This is the fact that during the OBE, they are convinced that what they are experiencing is actuality. For example, the gentleman with the "astral mother" whose case we have just discussed testified that he had learned through his OBEs that "the real Me is apart from and working through, my physical body. I now know for sure that we have two bodies."
This feeling of knowing "for sure" is quite characteristic of the tenacity with which people cling to the conclusions they draw from their out-of-body experiences. Wherever else they may differ, for instance whether the "two bodies" are or are not connected by a "silver cord," persons who have had out- of-the-body experiences are quite unanimous in being 'absolutely certain' that they are not dreams. Yet during ordinary dreams we are usually convinced at the time of the actuality of what we later discover to have been delusions.
An example of one of my own experiences is, I believe, especially revealing in regard to the similarities between dreaming and OBEs. Previously, I had had several lucid dreams in which I dreamed I could see my "sleeping body" in bed. I refer to them as "lucid dreams" rather than "OBEs" because that is how I interpreted them at the time. In my opinion " lucid dreams" and "OBEs" are necessarily distinguished by only one essential feature. This is how the person interprets the experience at the time. The primary qualification for an OBE is the sensation that a person is out of his or her body. Perhaps it would be less misleading to describe this experience as an "out-of-body sensation" (OBS) rather than an " out-of-body experience." So, if you believe, in some sense, that you are "out of your body," you are having, by definition, an "out-of-the-body" experience. This definition sidesteps the question of whether or not you have actually left your physical body. However, no experience guarantees the actual existence of the thing in question. In the dark forest, one may experience a tree as a tiger, but it is still in fact only a tree.
According to the traditional psychology of Tibetan Buddhism, all of our experiences are subjective, and thus, by their very nature, not in substance different from what we call " dreams. " This is also the point of view of the cognitive psychology of the modern West. Granting this premise, and scientifically speaking, it is impossible to argue with it, it would be difficult to name any experience that (by this definition) was not a sort of dream.
Consequently my assumption that OBEs were necessarily a certain species of dream, made the following experience all the more startling: aware that I was dreaming, the image of what I had been dreaming about faded, but I tried to hold onto it. Throwing myself into the darkness, I found myself crawling down a dark tunnel on my hands and knees. At first, I could see nothing, but when I touched my eyelids I was able to open them, and I suddenly found myself floating across the room toward Dawn, who was sleeping on the couch. I looked back to see my 'body' asleep on the living room floor. Somehow, I was completely convinced that this was not a dream, but that I really was seeing my sleeping body. Dawn awoke and started to speak and I felt myself magnetically drawn back into the body asleep on the floor. When I arrived, I got up in this body (which I took to be my physical body) and excitedly said to her, "Do you know what just happened to me? An Out-of-Body Experience of the genuine kind!" After this I was looking through a stamp book, when I found myself flying (like Superman) in the air over Germany.
I was shocked to awaken a few minutes later in my bed, and realize that I had been sleeping all along. By now my brain was working well enough to note the general implausibility of my previous interpretation of the recent events I had experienced. I could see, for instance, the inconsistencies implied by my belief that the body I had seen asleep on the floor, and entered from my supposed "other body" was actually my physical body. Were it not for the physical impossibility of traveling to Germany once I had opened a stamp book (though I owned nothing of the kind), and the contradictory waking testimony of Dawn, I might still be convinced that what had happened was not a dream. And this in spite of all 'reason' to the contrary. What we know for certain, reason is powerless to doubt. When you see your hand in front of you, can you really doubt that it is your hand? What we know for certain actually only means what we assume or believe we know. My "out-of-the-body experience of the genuine kind" serves as a reminder that we can be totally mistaken about what seems indubitable and certain.
The lucid dream is sometimes considered to be an inferior form of the out-of-body experience. But I believe the opposite may be the case, as may have already occurred to those readers who followed the progression of stages through which children pass in developing understanding of the concept of "dreaming". To briefly review what was said in Chapter 6, recall that at the earliest stage, children believe that dreams take place in the same (external) world as the rest of their experiences. Having learned, mainly through their parents, that dreams are somehow different from waking experiences, at the next stage they treat dreams as if they were partially external and partially internal. This transitional stage finally gives way to the third stage in which children recognize that the dream is entirely internal in nature, i.e., a purely mental experience.
These developmental stages refer, of course, to the conceptual terms with which children think about the dream after awakening. While dreaming, children and adults alike tend to remain at the first stage: implicitly assuming that the dream events are external reality. Likewise, "astral projectors" who explicitly believe that what they are experiencing is external reality would be at this same stage. However, most typical out-of-the-body experiences with their somewhat contradictory mixture of mental and material would seem to provide examples of the second stage. Only with the fully lucid dream does the dreamer arrive at the third stage of conceptual clarity: realizing that the experience is entirely mental and clearly distinguishing the dream from the physical world.
In support of the notion that OBEs are generally the result of a misinterpreted dream experiences, let me offer a personal observation. In about 1% of the approximately 800 lucid dreams in my record, I felt I was in some sense 'out- of-my-body.' In every case, when examining the experience after awakening, I noted some deficiency in either my memory or critical thinking during the experience. In one such situation, I tried to memorize the serial number of a dollar bill to verify later whether I had really been out of my body or not. When I awoke, I couldn't recall the number, but it hardly mattered. I now remembered that I hadn't lived in the house I thought I was asleep in for several years. In another instance, I was floating near the ceiling of my living room " looking at some photos on top of a cabinet that I knew I hadn't seen before, given by habitual confinement to walking on the floor rather than the ceiling! My hopes of verifying this paranormally gained information evaporated in a flash when I remembered upon awakening that I hadn't lived in this house for more than 20 years!
In contrast, during most of my lucid dreams I can remember where I am sleeping (if it matters) and usually have as accurate a notion of the date as I normally have while awake. Frequently, I know what time it is within a few minutes.
From this I suggest that imperfect brain function during REM sleep may at times give rise to incomplete lucidity during dreaming. This state is characterized by partial amnesia, inadequate reality testing, and interpreting the experience as being out-of-body rather than dreaming.
All in all, the quality of reasoning during OBEs seems to me to closely resemble Nietzsche's description of the reasoning typical of primitive humanity and also of dreamers today: " the first causa which occurred to the mind to explain anything that required an explanation was sufficient and stood for truth."  This pre-critical stage of mind is also typical of the explanations many pre-lucid dreamers accept as proof that they are not dreaming. I believe a similarly stage of mind characterizes the reasoning whereby people convince themselves that they really are "out-of- body."
In fairness, it should be pointed out that the manner in which OBEs are typically initiated makes the "out-of-body" interpretation of the experience seem almost beyond questioning: you are apparently awake in bed, and then, with no more notice than a feeling of vibration or melting, you find yourself "peeling," "stepping," or "floating" "out of the body." Most people accept uncritically that what seems to be the natural explanation is the explanation of the experience.
In accordance with Nietzsche's contention above,, "leaving one's body" is the first causa to occur to the dreaming mind, and it is accepted on face value as the explanation. One of the reasons people might be likely to label an experience like we've just described as "out-of-the body" rather than dreaming is because it seemed to happen while they were awake. Obviously, if they were asleep, they couldn't have been dreaming, and if they weren't dreaming, they must have been doing what it seems they were--being "out-of-the-body."
This all seems straightforward enough, except for one awkward fact: it happens that in a variety of circumstances, it may be extremely difficult to determine whether or not you really are asleep or awake, only dreaming or really seeing. These states of confusion are especially likely to occur during sleep paralysis, a condition that sometimes results when a person partially awaken from REM sleep and finds himself unable to move, because the part of the brain that prevents them from acting out their dreams for some reason temporarily continues to function even though they are otherwise "awake." Although the physiological basis for sleep paralysis has only recently been uncovered, the state and the hallucinatory experiences associated with it have been known for many years. For example, Eleanor Rowland described some of her experiences of this confusing blend of dream and reality in a 1908 paper entitled "A case of visual sensations during sleep":
" It often happens that dream persons issue from behind a real door, a dream hand moves along a real wall, and a dream figure sits upon the real bed. Since my vision is so accurate, I can not reassure myself by being certain that I am asleep. Nor am I in a slumber deep enough to accept any dream that comes without comment. My reasoning powers are active at such times, and I commune thus with myself: "No one can have opened the door, for you know you locked it." "But I see a figure distinctly standing at my elbow, and it has knocked on the door twice." "You are probably asleep." "How can I be? I see and hear as distinctly as I ever do." "Why then, don't you push the figure away?" "I will. Here I am doing it." "No--you are not doing it at all, for you can see that you have not moved an inch." "Then I am asleep after all--the figure is not there, and I need not be afraid of it." 
The lesson to be learned from all this is that it is not always easy to determine which world you are living in at any given time: telling dreams from reality is no easy matter. Neither biological nor cultural evolution has prepared you to any significant extent for this particular task. Distinguishing one state of consciousness from another is a cognitive skill learned in exactly the same way that you learned as children to comprehend the gibberish of sounds that became your native language--by practice. The more practice you gain in lucid dreaming, the easier you will find it not to be fooled into thinking you are awake when you are dreaming. The more experience you have had with recognizing false awakenings, sleep paralysis, and other phenomena associated with REM sleep, the more likely it is that when you "leave your body" you will recognize it as a lucid dream.
This, in fact, is what we have observed with most of our experienced oneironauts. They quite frequently describe lucid dreams initiated from brief awakenings within REM periods as " leaving their bodies " even though we all agree that while this terminology effectively captures the way the experience actually feels at the time, it does not presumably describe what really happens.
As an example of the peculiar form typically taken by these experiences, consider one of Roy K.'s laboratory lucid dreams: while lying on his right side, he began turning to the left and felt as though he had "left his body." He saw a scene of a field and signaled lucidity about seven times. Next appeared a glowing, reddish light, so he turned to the right towards it, and flew down an alley. At this point, he resumed signaling although he was later unsure of exactly how many times he had moved his eyes. It might have been nine. In any case, he continued to fly down the alley until he saw the moon--full and strikingly luminous. Upon seeing the stars above, he decided to try to unite them with the moon. But it was too late. Already he felt his body paralyzed in bed. He wanted to wake up and signal someone, and after what seemed like a very strenuous effort, succeeded in awakening and pressed the call button.
Before I offer an explanation for what I believe may actually be happening in experiences of this kind, I would like to describe one of my own wake-within REM initiated lucid dreams. It was the middle of the night, and I had evidently just awakened from a REM period since I effortlessly recalled a dream. I was lying face down in bed, drowsily reviewing the story of my previous dream when I suddenly experienced a very curious sensation of tingling and heaviness in my arms. They became so heavy, in fact, that one of them seemed to melt over the side of the bed! I recognized this distortion of my body image as a sign that I was re-entering REM sleep. As I relaxed more deeply, I felt my entire body become paralyzed although I could still seem to feel its position in bed. I reasoned that this feeling was most likely a memory image and that actual sensory input was cut off just as much as motor output. I was, in short, asleep. At this point, I imagined raising my arm and experienced this imagined movement as if I had separated an equally real arm from the physical one I knew to be paralyzed. Then with a similar imagined movement I, as it were, "rolled out of my physical body entirely." I was now, according to my understanding, wholly in a dream body in a dream of my bedroom. The body I had seemed to leave and which I now dreamed I saw lying on the bed, I quite lucidly realized to be a dream representation of my physical body; indeed, it evaporated as soon as I put my attention elsewhere. From here, I flew off into the dawn....
I would say that having awakened from REM sleep, I was (as always) experiencing my body image in a position calculated by my brain. Since this calculation was based on accurate information about the physical world obtained through my awake (and therefore functional) senses, my experienced body position corresponded to my actual situation of lying in bed. Since during sleep (particularly REM), sensory input from the external world is actively suppressed, at this point my sensory systems no longer provided my brain information regarding the physical world. Thus my brain's representation of my body-image was no longer constrained by sensory information concerning my body's actual orientation in physical space. I was consequently free to move my body image in mental space out of the position it was represented as being in when last in sensory contact with the physical world. I could in fact now move this image to any new position in mental space that I chose. With no sensory input to contradict any imagined position of my body image that my brain cared to construct, I could freely "travel" anywhere in mental space.
Let us consider, for comparison, an alternative theory: OBEs as "astral projection." The idea of the astral world was brought to the West and popularized by Madame Blavatsky in the last century. According to her doctrine of Theosophy, the world is composed of seven planes of existence: each plane is made up of atoms of varying degrees of refinement. The physical world is the coarsest of all. On the next higher level, the so-called "etheric" plane, we find a second body-- but this is not yet the "astral body," only the "etheric body" normally attached to the physical body and serving to keep all seven bodies in communication. The next higher plane is the "astral" where we find the body we have been looking for. The astral world is made of "astral matter" which is superimposed on physical matter, and everything in the physical world has its counterpart in the astral world. However, there are more things found on the astral plane than on the physical including a menagerie of spirits and elementals and discarnate entities of all sorts. What is most to the point here is that the astral body was supposed to be able to travel on the astral plane free of the physical body, and since the astral was supposed to contain a copy of everything in the physical world, it would have seemed an easy matter to gain information from distant places by speedy travel on the astral plane. There are many difficulties with the "astral world" theory of dreaming and OBEs. Just to name one, I can recall lucid dreams in which I viewed a dream representation of my bedroom that was missing a good deal of " astral" matter: a whole wall and window in fact! But my intention here is not to expound the theory of astral projection, but only to translate their terms into mine.
What occultists have termed "astral travel," I am calling " mental travel". Moreover, instead of "astral world," I say " mental world"; and as for the mysterious entity elsewhere referred to as the "astral body", "double", or "phantom", or " second body", I regard it as an experiential reality that I have identified with the body image, but the most straightforward term for it may be "the dream body."
This dream body is our mental representation of our actual physical body. But this is the only body that we ever directly experience. We know by direct acquaintance only the contents of our minds. All of our knowledge concerning the physical world, including even the assumed existence of our " first" or physical bodies, is by inference.
Just because our knowledge of external reality is indirect, it should not lead us to conclude that mind alone exists or that the physical world is merely an illusion. Due to its representational nature, it is our mental world that is the illusion. Our mental experiences can be compared to watching television. The televised events are merely projected pictures having only the semblance of reality. Whether or not the events we see on television have any correspondence with actual events is another matter. When, for instance, we watch a news program we trust we are witnessing the depiction of events that actually occurred in physical reality. If we have seen a man killed we expect him to be in fact--dead. In contrast, when we see an actor "killed" in a television melodrama, we consequently expect him rather than his widow to collect his pay check!
In both of these cases, what we experienced were illusions in the sense that the events that apparently took place on our television were only the images of events that may or may not have actually occurred in external reality. This is the necessary condition of all of our experiences: as mental representations, they are the images of the things they represent--not the things themselves. It is much more informative to specify the relation between the image and the thing it represents. Our two examples represent opposite degrees of possible correspondence. In the case of the actor, there was no relationship between the theatrical "death" portrayed and actuality. In contrast, the news program showed us the image of an event that precisely corresponded to the occurrence of an actual event. Thus we accept the news as accurately expressing reality. One can easily imagine television productions possessing degrees of truth anywhere between the two extremes we have considered, such as a dramatic enactment of a true story or a news program that mistakenly reported that a man had been killed when he had in fact only been wounded.
Now imagine a person confined to a room whose entire experience of the outside world is limited to what he or she sees on television. Such a person might well regard television as the primary reality and "the outside world" as a derivative and unnecessary hypothesis.
I am suggesting by this metaphor that we are all in a very similar situation: the room we are confined in corresponds to our minds, and the television programs to the news and fantasies of the external world, brought to us by our senses. All of the foregoing discussion in reference to television images equally applies to the mental images out of which we construct our worlds.
In the terms I have proposed here, being in the body means constructing a mental body image. Because it is based on sensory information, it accurately represents the body's actual position in physical space. While dreaming, we are out of touch with our bodies and consequently liberated from the physical constraints imposed by waking perception. Thus no awkward sensory facts are present to limit our movement in mental space, and we are free to move out of the spatial orientation defined by "being in the (physical) body."
The part of us that "leaves the body" travels in mental, not physical space. Consequently, it would seem reasonable to suppose that we never "leave our bodies" because we are never in them. Where "we" are when we experience anything at all-- OBEs included--is in mental space, not physical space. Milton's famous phrase, "The Mind is its own place," goes not quite far enough. The mind is not merely its own place, the mind is its only place.
We are ready to address an empirical aspect of the OBE phenomenon. Persons undergoing OBEs frequently believe they are paranormally perceiving happenings taking place in the physical world. Unfortunately, in most cases, this belief takes the form of an untested assumption. Like the events we see on television, what we see during OBEs could have any degree of correspondence with physical reality.
The generally unquestioned assumption underlying OBEs is that the person having the experience is actually situated, in some unexplained way, elsewhere in the physical world than in his or her physical body. An implication of this is that what the person sees while "out-of-the-body" ought to be an accurate reflection of physical reality, entirely analogous to ordinary perception. Rarely are either of these assumptions subjected to rigorous test or, for that matter, to any test at all. These are empirical questions that can and should be settled by scientific experiment.
Are there any scientific data that might allow us to arrive at a verdict on the claim that OBE vision is valid? There is in fact a good deal of relevant evidence available and there have been a number of studies of OBE vision that meet the standards of rigorous control required by exact science.
There are two ways of broadly viewing the results of these studies. First of all, we have the summary of Karlis Osis, Director of Research at the American Society for Psychical Research (A.S.P.R.). This society, in an effort to produce evidence for survival of death, undertook an extensive investigation of OBE perception.  In the course of this study, approximately 100 subjects, all of whom believed they were proficient in inducing OBEs and possessed paranormal perceptual abilities during these OBEs, were tested under controlled conditions. While confined to one room at the A.S.P.R., the subjects induced OBEs and "visited" a distant target room, attempting afterwards to describe in detail what they had "seen" while there. A comparison of their reports with the actual contents of the target room revealed, in all but a few cases, absolutely no indication of any correspondence whatsoever. In other words, in the great majority of these cases, there was no evidence supporting accurate OBE perception, nor for the validity of the subjects' convictions that they had actually left their bodies. Moreover, these subjects were described by Osis as being "the creme of the claimants" of OBE. I believe the results of this study strongly supports the "OBE as misinterpreted lucid dream" interpretation offered above.
As for OBE vision, in the words of Dr. Osis, "the bulk of the cases seem to be a mirage." At best, OBE vision seems a highly variable and unreliable mode of perception "ranging from fairly good (i.e., clearly distinguishing some objects) to complete failure (i.e., producing very foggy or totally incorrect images)." Moreover, Osis added, "of those individuals in our studies who have shown some signs of OOB perceptual power, we did not find a single one who could see things clearly every time he felt he was out of body."
The great majority of alleged cases of OBE vision apparently show no greater degree of perceptual ability (in regard to the external world) than we would expect from ordinary dreams. This might by itself suggest that the nature of OBEs would require no additional explanation than that already discussed.
But the existence of even occasional exceptions of apparently accurate OBE perception is a fact that still needs to be explained. The traditional explanation holds that OBE vision is a form of direct perception by means of the senses of a non-physical body. There is an alternative explanation that is philosophically sound, economical, and (most importantly) in agreement with observation. It does not in the first place assume a condition of unvarying accuracy during OBE or lucid dream vision. Instead, it suggests that like all other mental imagery, this form of perception may be relatively more accurate at some times than others. Mental experiences can be ordered on a spectrum ranging from little or no relation to external reality (e.g., "hallucinations") at one end, to near perfect correspondence with actuality (e.g., "perception") on the other end. Moreover, there can be any degree of relationship in between, and it is somewhere in this middle ground that dreams and OBEs generally reside.
What I am proposing is that the select minority of accurate OBE reports are simply cases of dream telepathy. To some people, this may seem like explaining the mysterious in terms of the more mysterious. Dream telepathy is a fact only barely established and in no way satisfactorily understood or explained. A question for future research is whether lucid dreamers and OBErs are more conducive to telepathy than ordinary dreamers.
Taking together the out-of-body experiences with which we have become familiar, they do not seem to have lived up to the claim that they would "challenge our most basic assumptions concerning the nature of reality." Perhaps only dream telepathy so far has provided us, so far with any significant fact of the kind that makes us ponder deeply or gaze into the starlit night. I have saved for last what may be the most mysterious of the reality-shaking phenomena of the world of dreams: I am referring to what are variously called "mutual," "reciprocal," or "shared" dreams.
These are the perplexing experiences in which two or more people report having had similar if not identical dreams. In some of these cases, the reports are so remarkably alike that one is almost compelled to conclude that the dream sharers appear to actually have been present together in the same dream environment. If this does occur, it would imply that at least under certain cases the dream world and likewise the dream bodies within it could possess some sort of objective existence. On the other hand, in mutual dreams we may only share dream plots, not the dreams themselves. Let us examine a classical account of ostensible "reciprocal dreaming."
In Elmira, New York, on Tuesday the 26th of January, 1892, between 2 and 3 A.M., Dr. Adele Gleason dreamed that she stood in a lonesome place in the dark woods and that great fear came over her, at which point she dreamed that John Joslyn, her attorney and friend, came to her and shook a tree by her, causing its leaves to burst into flame. When the two friends met four days later, Adele mentioned having had a " strange dream" last Tuesday night. John stopped her at once replying, "Don't tell it to me. Let me describe it, for I know that I dreamt the same thing." At approximately the same time on Tuesday night as Adele's strange dream, John had awakened from a no less strange dream of his own and written down the following remarkably similar account: he had found Adele in a lonely wood after dark, "apparently paralyzed with fear of something I did not see, rooted to the spot by the feeling of imminent danger. I came up to her and shook the bush, upon which the leaves that fell from it burst into flame." 
Although these two dream reports are remarkably similar, they are not quite identical. For example, Adele made a tree of what for John was only a bush; Adele's leaves burned on her tree, while John's turned to flame while falling. The original reports show other discrepancies as well. I would interpret this as an instance of shared dreaming as caused by Adele's telepathic transmission to her friend of an s.o.s., along with the highly-charged imagery of her dream. John, for his part, responded in his dream to his friend's call for help, by telepathically initiating and sharing a visionary experience strikingly reminiscent of the Burning Bush of Moses. This is a truly amazing tale of two dreams, yet it does seem to me to more strongly support the hypothesis of shared dream plots rather than shared dream worlds.
A somewhat more convincing anecdote is provided by Oliver Fox: "I had been spending the evening with two friends, Slade and Elkington," wrote Fox, "and our conversation had turned to the subject of dreams. Before parting, we agreed to meet, if possible, on Southampton Common in our dreams that night." Later that night, Fox claimed that he dreamed that he met Elkington on the common "as arranged." So far, so good, "but Slade was not present." According to Fox, both he and Elkington both knew they were dreaming, and commented on Slade's absence. "After which the dream ended, being of very short duration." Fox tells us that when he saw Elkington the next day he kept quiet and asked him whether he had dreamed. " Yes," Elkington replied, "I met you on the Common all right and knew I was dreaming, but old Slade didn't turn up. We had just time to greet each other and comment on his absence, then the dream ended." This, to Oliver Fox's mind, "perhaps accounted for" Slade's "inability to keep the appointment." What happened to Slade? Fox was able to settle the mystery to his own satisfaction at least. When they finally found Slade and asked him what happened, he replied that he "had not dreamed at all." 
Intriguing as this particular case appears, it is marred by Fox's failure to report the exact time of occurrence of the two lucid dreams. Although the dreams are described as occurring on the same night, if they happened at different times (i.e., if Fox and Elkington were not in REM sleep at the same time), it would favor the hypothesis of shared dream plots over being in the same dream at the same time. In any case, Fox was unable to repeat "this small success" in mutual lucid dreaming and expressed the belief that "it is an extremely rare occurrence for two people to share approximately the same dream experience."
The examples we have so far considered were both once-in-a lifetime experiences for the dream sharers. In contrast, there are suggestions that mutual dreaming abilities have been cultivated to a high level by a number of Sufi mystics. Aside from various stories of Sufi masters being able to appear in the dreams of anyone they chose, there is the report of a group of dervishes who explored the world of dreams on the island of Rhodes in the 16th Century.  The dervishes were presided over by a Sheikh, "a certain Hudai effendi" who not only "practiced all the virtues, cultivated all the sciences and read books in the majority of Classical languages" but "devoted himself to the cultivation of collective dreams." In an isolated monastery atop a small hill on the island, "master and disciples purified themselves bodily, mentally and spiritually together; they got into an enormous bed together, a bed which contained the whole congregation. They recited the same secret formula together and had the same dream."
A remarkable story is told of an encounter between the dream master of Rhodes and Suleiman the Magnificent, the Sultan of Turkey. One day, during a military campaign in Corinthia, Suleiman found himself in a seemingly impossible dilemma. Neither the Grand Vizier nor any others of the Sultan's corps of advisors could devise any plan of action whatsoever. Fortunately, the Sultan remembered that there was still an emissary of Hudai effendi in his camp. Since the dream-master had helped him in the past out of no less difficult circumstances, Suleiman summoned the dervish, and providing him with travel expenses, and safe conduct passes, asked him how many weeks he would need to journey to Rhodes and return to the Imperial camp with the Sheikh.
"The dervish gave an involuntary smile. 'Sire,' he replied, 'I thank you for the travel expense and the safe-conducts. I have no need of them. True, to the vulgar the island of Rhodes is far from here, but the venerated Sheikh Hudai is no distance from Your August Highness's camp. I undertake to summon him tonight, even before morning prayers.'"
Misunderstanding the nature of the Sufi's nearness, the Sultan was "astonished at the holy man's presence in the neighborhood of his camp," and gave the dervish purses full of gold and silver, but he refused them. In return, the dervish offered Suleiman a "soporific apple" which the Sultan peeled and ate.
"Then the mysterious man went so sleep," as did the Sultan also. Previously he had ordered him men to awaken him at the arrival of Hudai effendi. But when the master failed to appear, they laughed at the dervish and mocked their " Sovereign's credulity and senility." When at dawn the muezzin of the army began the morning call to prayer, The Great Eunuch gently awoke the Emperor and after wishing him good morning as well as a brilliant victory over the enemy, whispered ironically: "Sire, no news of Sheikh Hudai effendi. It looks as if his disciple is a fraud."
"Silence, you utter imbecile," roared the Sultan, "silence! The illustrious Master has deigned to visit me. I have had a long conversation with him and I tell you that my faithful armies have won the most brilliant of victories, less than an hour ago. Await the messenger's arrival." The enemy commander had passed out just at a crucial moment as the battle was about to begin and his subordinates were unable to carry on without him, with the result as foretold by the Sultan via Sheikh Hudai.
Evidently, "at a dream signal from the humble disciple" Hudai effendi had visited and advised Suleiman--in a dream! Moreover, there is the suspicion that the dream master may have been somehow involved in the enemy commander's mysterious and for him ill-timed loss of consciousness which resulted in what would seem "the most accidental" in spite of being called "the most brilliant of victories" for the armies of Suleiman the Magnificent.
Fascinating as this and other anecdotes of mutual dreaming may be, they bring us no nearer to deciding between the competing interpretations of actually shared objective dream- worlds vs. paranormally shared but subjective dream-plots, resulting in correlated content in separate dreams. One might wonder whether there is any way that the question could be definitely settled. I propose that there is in fact an empirical test that could distinguish between the two possibilities: two oneironauts would have simultaneous lucid dreams while being monitored in a sleep laboratory. They would agree to meet in their lucid dreams and signal simultaneously by, for example, both following with their gaze the movement of one of their hands, back and forth, left and right. If the strong interpretation is of mutual dreams, i.e., if the lucid dreamers are actually sharing a dream- world, they would show simultaneous eye-movement signals in their polygraphic recordings. If on the other hand, they report carrying out this task in a mutual lucid dream and do not show simultaneous signals, we would have to conclude that they were at most sharing dream plots. Let us be sure to appreciate the significance of such an experiment. If the mutual lucid dreamers fail to show simultaneous signals, it would be neither surprising or especially significant. However, if the mutual lucid dreamers did prove to produce simultaneous eye movement signals, we have incontrovertible proof for the objective existence of the dream world. We would then know that, in certain circumstances at least, dreams can be as objectively real as the world of physics. This would finally raise the question of whether physical reality is itself some kind of mutual dream. Perhaps what really happens is the balanced result of a myriad of interactions contributed by us all dreaming the dream of consensus reality. But if not, then there's always Bob Dylan's offer: "I'll let you be in my dream, if I can be in yours."
 Nietzsche, F. HUMAN, ALL TOO HUMAN, aphorism #5.
 Celia Green (1967) asked two samples of undergraduates from two British universities whether they had ever had an " experience in which you felt you were 'out of your body'"? She received 19 percent positive responses out of 115 in the first sample and 34 percent positive responses out of 380 in the second. Hornell Hart (1954) received 27 percent positivereplies from 155 Duke University sociology students, while Charles Tart (1971) received 44 percent positive responses from 150 experienced marijuana users. In D. S. Rogo [Ed.], MIND BEYOND THE BODY. New York: Penguin, 1978, p. 36.
 Rhine, L. E. Psychological processes in ESP experiences. Part II. Dreams. JOURNAL OF PARAPSYCHOLOGY, 26:172-199, 1962.
 Sheils, D. A cross-cultural study of beliefs in out-of- the-body experiences, waking and sleeping, JOURNAL OF THE SOCIETY FOR PSYCHICAL RESEARCH, 49:697-741, 1978.
 Priestly J.B. MAN AND TIME. Aldous Books, 1964, p. 225-6.
 Ullman M., Krippner S. DREAM TELEPATHY. New York: MacMillan Publishing Co., 1973, p.111.
 Of the 13 experimental studies carried out, 9 yielded statisically significant results. Replications in laboratories elsewhere yielded less consistent results: two were positive, three negative, and one equivocal.
 Rogo, D.S., Introduction: Autobiographical accounts, from Rogo, D.S., (ed.), MIND BEYOND THE BODY (New York: Penguin, 1978), pp. 248-49.
 Harary S.B. A personal perspective of out-of-body experiences. In Rogo, op. cit., p.248-9.
 Ibid., p.356-7.  deBecker R. THE UNDERSTANDING OF DREAMS. London: Allen & Unwin, 1965, p.249.
 Rowland, E. A case of visual sensations during sleep, THE JOURNAL OF PHILOSOPHY, 6 (1909): 353-57.
 Osis K. Perspectives for out-of-body research. PARAPSYCHOLOGY RESEARCH. 3:110-13, 1973.
 deBecker, op.cit., p. 394-95.
 Fox O., ASTRAL TRAVEL. New York: University Books, 1962, p.47.
 DeBecker, op.cit., p. 76-78.