Freud postulated that dreams reflected unconscious wish-fulfilment, desires which often related to childhood experiences. The nature of these motives was predominately sexual. However, he later posited that trauma, aggression and even supernatural factors could also influence dream content.
Like Freud, Jung believed that dreams arose from the unconscious mind, but rejected the idea that their meanings were distorted and hidden under layers of unconscious symbolism. Jung argued that what we experienced during sleep were messages, which if understood, could resolve emotional and religious problems as well as alleviate fears. Jung also coined the phrase day residue - waking memories that form impressions for the unconscious to reenact during sleep. Every dream character represented an aspect of the dreamer. Fritz Perls expanded on this by arguing that even inanimate objects were representations of an aspect of the dreamer.
J. Allan Hobson and Robert McCarley argued that circuits in the brain stem were active during sleep, which activated areas of the primordial limbic system - involved in emotions, sensations and memories. Changes in the physical environment and physical stimuli create signals, from which the brain attempts to find meaning. Dreams are the brain's attempt to extrapolate meaning from neural activity.
Research by Mark Solms suggests, however, that source of the signals and thus the source of dreams was not the brain stem. He studied patients with various brain injuries. He found that damage to the brain stem did not affect the patient's ability to dream. He discovered patients with injuries to the parietal lobe stopped dreaming, indicating that it was this area of the brain that produced the signals that would constitute the fabric of dreams.
Jie Zhang proposes that the function of sleep is to process, encode, and transfer data from temporary memory stores to long-term ones. The brain processes conscious memories (declarative memory) during non REM sleep and processes unconscious memories (procedural memory) during REM sleep.
While the brain is processing procedural memory, the activity of the conscious part of the brain is low. The disconnection of sensory systems triggers the "continual-activation" mechanism. This system streams data through the conscious part of the brain, inducing dreams. Zhang maintains that each pulse of data involves the brain's associative thinking system. The dreamer can actively engage with the dream-scene until the next pulse of memory-data, and the scene changes. This theory accounts both for dream continuity and sudden changes in dream content.
Several theorists such as Flanagan and Hobson regard dreaming as a random by-product of REM sleep, devoid of any purpose. They are "evolutionary epiphenomena".
Deirdre Barrett believes dreams serve as an adaptive function for survival. Dreaming constitutes thinking in a different biochemical state.
Antti Revonsuo posits that the purpose of dreams is to prepare the dreamer for real-life threats, whether physical or interpersonal. Revonsuo argues that this is why an average person experiences threats of a much higher magnitude than they would in their waking lives.
While more recent empirical evidence has debunked some of the older theories, it is clear that we are some ways from an agreed-upon answer to the function of dreams - if there is one at all.
Whatever the function of dreaming, it provides an opportunity to explore and push the limits of your imagination. We spend one-third of our lives asleep. We can ignore our experience of this time, or we can cultivate it and ingrain it into our conscious memory.