Jung’s theory on this is what he coined the “collective unconscious” which is a well of patterns, stories and themes all humans share. And it relates to a personal unconscious which elaborates on these themes within an individual’s experiences and social context. Dreams and manifestations of schizophrenia are similar in that they act out these patterns and make them conscious to the dreamer/sufferer. A difference is the dreamer wakes up and realizes it’s a dream, whereas a person with schizophrenia experiences the unconscious content while they are awake—assuming it’s all real.
Dreams may all seem different to dreamers, because they are focused on personalized specifics of dream content. Just as people with schizophrenia are heavily focused on the specifics of their delusions. In my case the story of the FBI following me was all in the personal details, how they came to follow me, why they wouldn’t go away, how I became aware of them, steps I took to communicate to them, what they had done/are doing/would do to me, etc. These details are meaningless and at times nonsensical to outside observers, because first, they don’t accept the premise that the details are real, and second they lack the back-story context that makes these details “real” to the person with schizophrenia. They all sound the same, and the details don’t matter. Yet in a hospital context, we might pick apart another patient’s story as “crazy” while professing ours to be completely “normal”. My experience is folie a deux is less common than you’d think. Caregivers often don’t take the time and considerable effort it takes to extract and understand the point of view of the sufferer. Dr. Amador’s LEAP process offers a practical (if laborious) way to get at this information for lay people.
While I was in analysis my therapy alternated between talking about my life and bringing in dreams to discuss. Some dreams were less useful than others, just as I’m sure some of you have bizarre dreams that seem like cleaning out the garbage of experiences from days or events before. Sometimes I would have “diagnostic dreams” which were interesting to my therapist and we’d talk about them at length and she’d ask me about details and what they meant to me.
Similarly I expect you’ve had dreams with similar patterns to other people and perhaps your own—you just think no one else has them because you are focused on the details and not overall patterns. To illustrate this, here’s a recurring dream I have: I’m backstage at a theatre and I have to perform in a play I’m unfamiliar with and in a role I don’t know. A variant of this might add that I have to perform nude or in my underwear or otherwise embarrassing or compromising position. This may seem very specific to me as an actor, but it’s essentially the same as the unexpected test, or exam, or report, or speech, or job presentation dream countless people have had. Or the “being vulnerable in public” dream many people have. In these simple examples the “collective unconscious” part might be “fear of being unprepared” or “fear of being exposed” and the personal and social elaborative context might be the setting or the audience or the subject.
One way to think about it is the collective unconscious is a set of outlines, stock characters and tropes, and the personal unconscious is the experiences and settings that we as dreamers use to write our own stories as dreams. When you have active schizophrenia the stories manifest as more elaborate delusions, since you can “write” more complex narratives when you are effectively dreaming 24/7 and while conscious can retain much more of the dreams that dreamers quickly forget, so delusions can be truly “epic”.
Joseph Campbell built on Jung’s work and wrote “The Hero With a Thousand Faces” which posits that essentially all of mythology is parts of a universal mono-myth retold over and over and spans cultures millennia. He writes mainly about the universal “hero’s journey”, but also other common recurring stories about creation, salvation; destruction ( ex. flood stories) and oblivion (ex. Armageddon). His work in turn inspired George Lucas to create the Star Wars myth as a myth for modern times.
This is all a gross oversimplification of Jungian thought, and I don’t profess to be an expert or its efficacy for other people or as a treatment for schizophrenia. One of the first questions my analyst asked me was how much I knew about Jungian Psychology, and I said “not much”. She said it didn’t matter, I didn’t need to know anything about it for it to work.
I know more now, but bear in mind Jungian Psychology predated modern psychopharmacology and my psychologist required I be evaluated by a psychiatrist for treatment prior to working with her. It has its flaws and is not a panacea, and isn’t particularly useful in those without insight. It was developed before we had drugs and brain imaging and the like, and there’s now a post Jungian movement which seeks to merge Jung’s ideas with modern neuroscience and research on consciousness. I don’t post about Jungian theory much other than mention my Jungian therapies, as it’s not as universally helpful as psychiatric treatment and LEAP, but it serves to help offer possible explanations to your questions.