There is a wide span of theories that are both popular and accepted depending on who you ask—ranging from the view that “dreams are purely physiological and originate in the brain” to the view that “dreams are the true reality and waking life is the dream” –and everything in between.
On the more physical end of the spectrum, some neuropsychologists say dreams come from shifts in brain chemistry, and that dream experiences happen “all in your head.” Other neuropsychologists say most of our dreams originate in this way, but not all dreams. There’s plenty of evidence to support the idea that a dreamer could experience an entire ‘dream universe’ that is isolated from other people and places.
However, this way of thinking about dreams doesn’t account for extraordinary dream reports such as: out-of-body, collective, telepathic, clairvoyant, pre-cognitive, and spiritual visitation dreams. Lucid dream experts continue to explore and debate whether or not dreamscapes are shared or separate, and some say it depends on the dream.
Sigmund Freud purported his theories about dreaming were all-inclusive and not to be challenged by his successors. In general, he said dreams come from unconscious wishes, desires, and sexual complexes. His groundbreaking contributions are a piece of the puzzle, and there are still many Freudians, but his perspective has become much less popular than it was earlier in the 20th Century.
Carl Jung discarded Freud’s theories because he didn’t agree that they were all-inclusive. Jung, who felt dreams transcended wishes, desires, and sexual complexes—said dreams come from the Collective Unconscious, and that every dream is a unique process of discovery. Jung had himself experienced many extraordinary dreams since childhood. He was a world-traveler, interested in universal aspects of dreaming from culture to culture. Modern-day Jungians work with symbols and archetypes in dreams, and for decades now Jungian theory has outnumbered Freudian theory in popularity.
From the more spiritual end of the spectrum, it’s well documented that ancient civilizations including Sumeria, Egypt, and Greece relied on dreams to receive spiritual knowledge, guidance, and healing from the Gods and Goddesses of their cultures. Many indigenous cultures have said dreams originate in the spirit world and are either equal to, or greater than waking life in value and importance. Some examples are the Senoi of Malaysia, the Mapuche of Chile, the Guanari of Brazil, the Aborigines of Australia, and Native American tribes such as the Iroquois, the Menominee of Wisconsin, and more. An Apache-Pueblo shaman once taught me that the dream is to be regarded as Great Spirit—and in that world-view, is to be treated as an entity… therefore etiquette is required, such as an offering of tobacco for receiving a powerful dream.
Probably the furthest theories from neuroscience are those of shamanic dreamers, dream journeyers/dream travelers, which say souls and/or spirits travel outside the physical body—that people actually go on journeys when dreaming. Examples with this viewpoint range from tribes such as the Chiquitano of Bolivia, to Western followers of the ideas of Rudolf Steiner, and Robert Moss. Western advocates of these dream theories usually respect research on the dreaming brain, but tend to see the brain less as the ultimate source and container of dreaming, and more like a control tower that is active during dreaming while the dreamer is not isolated from the rest of the cosmos.
Sometimes dream researchers get very passionate about their particular position, and promote their ideas conclusively, as Freud did. Others see that all of the above theories are possible, depending on the background of the dreamer’s cultural influences and world-view.