In my experience, there are roughly three different views one can take to spiritual experiences such as summoning demons or talking with spirits:
1. The credulous view: According to this view, the spirit world is literally real and has an existence outside of the human mind. When you “summon” a spirit, a real entity will actually appear and speak with you. You can get information from spirits that you wouldn’t have known yourself.
2. The skeptical view: According to this view, the spirit world has literal existence out of the human mind. It’s “all in your head” and is therefore not real. Anyone who claims to have spoken to a spirit is either lying, or deluding themselves. You may “hear” a spirit in your head, but it’s really just your own thoughts, and can’t tell you anything you don’t already know.
3. The psychological view: According to which, spiritual phenomena is “all in your head,” but is still real and meaningful.
I think #1 and #2 are fairly self-explanatory, with a few caveats. First of all, these are general attitudes toward spiritual phenomena, not “types of people.” Someone may hold a credulous view towards one claim, and a skeptical view towards another. Even if a believer is “credulous” in general, it doesn’t mean they automatically believe everything they hear; and even if a staunch materialist is “skeptical” in general, it doesn’t mean they won’t believe a seemingly fantastical claim, if given sufficient evidence. Many people in the occult scene seem to fall somewhere in between these two. Someone might claim to regularly see and speak with spirits, but if pressed, they will admit they only see them “in the mind’s eye,” not physically. Yet, there are also those who see and hear spirits with their physical senses - what would commonly be termed “hallucinations” according to the skeptical or materialist view. And I’m sure some people experience both, at different times.
So, what about this “third view”? This is a view that while there is no evidence of the spiritual world physically or literally existing outside of the human mind, spiritual experiences are still real and meaningful to the people who experience them. In my opinion, there is no strong conflict between this “psychological view” of spiritual phenomena, and the more traditional “spiritual view.” The difference lies in how the experiencer conceives of the experience, but the actual experience itself is largely the same, regardless of if the experience is perceived to be “psychological” or “spiritual” in nature. For example:
Atheist Alice casts a spell to attract money. The next day, she finds $50 on the ground. She may write it off as a coincidence, but if she keeps casting spells and they consistently work, she eventually reasons that magic works by a sort of psychological mechanism. By casting a spell, she primes herself to focus on her goals be on the lookout for opportunities. Magic doesn’t create the opportunities, just helps her notice them.
Believer Bob casts a spell to attract money. The next day, he finds $50 on the ground. He may write it off as a coincidence, but if he keeps casting spells and they consistently work, he eventually reasons that magic works by a sort of spiritual mechanism. By casting a spell, he attracts the attention of the spirit world and raises his own power to achieve his goals. Magic creates the opportunities, but he still has to notice and take advantage of them.
(Even the most devout believers I have met acknowledge that some effort is required on your part; i.e. a spell to attract love is unlikely to succeed if you never leave your house and go meet people.)
In other words, for those who practice magic, the end result is generally the same regardless if they take an “atheistic” (psychological) or “theistic” (spiritual) approach to explaining the mechanism behind it.
The real question not whether a phenomenon has an external reality or is all in your head, but whether you should care. Is it something that requires your attention, or not? Let’s say you have auditory hallucinations telling you to jump off a bridge. However, you find that you can easily dismiss them. You ignore the voice and nothing bad happens. In this case, you may accurately describe the voice as not real and unimportant. Or perhaps the voice does bother you, but you get rid of it by taking antipsychotics. You conclude that the voice was psychologically constructed in nature, since you got rid of it via psychological means.
But, let’s say you are persistently bothered by the voice and vision of a certain spirit. Ignoring it doesn’t make it go away. Taking antipsychotics doesn’t make it go away. Yet, you are able to deal with it using spiritual means – either by attending to the spirit and giving it what it wants (if it’s benign), or perhaps doing a banishing ritual or exorcism to get rid of it (if it’s malignant). Again, the materialist would say that it’s all a hallucination, and even the “spiritual” means only worked because of psychological reasons (e.g., they work because you expect them to work). Once again, however, this experience being “all in your mind” is essentially indistinguishable from “actual” spirit possession, regardless if it’s technically psychological in origin.
There is also a popular belief that spirits do exist as external entities, not as individuals necessarily, but as a sort of “force” or part of the “collective unconscious,” which can be tapped into by using the names, sigils, or images we associate with them. It is sometimes said that the names we use for demons or other spirits aren’t their “real” names, but more like signposts that help us locate them in the depths of the collective unconscious. Then when you invoke them, they appear to you in a personified form that makes them easier to comprehend and deal with, according to your cultural context. For example, a Christian may see Jesus, a Hindu may see Krishna, and a Satanist may see Satan. And again, there is a debate about whether these forces really exist “out there,” or if we are just getting in contact with internal psychological states that exist within us, or somehow a mix of both. I’ll admit, I haven’t read much Jung and have only a surface level understanding of the collective unconscious idea, so I’ll leave it at that for now.