Human psychology is formed through interactions with other humans.
In both complex and simple interactions with others, we often are forced to imagine what is happening. This is especially true in complex interactions.
Since what we imagine is often wrong, or wrong often enough to matter, our sense of who we are and who others are is largely deluded.
Humans do well enough in simple interactions involving formal rules. These are our public interactions that rely on the rules of our professions, clubs, churches, workplaces, etc. Even still, we are often wrong about what is happening in these settings, what our roles are, what others are thinking.
Complex interactions—that is, complex psychological interactions—are even more fraught with error than simple interactions. Indeed, they so fraught with error we can say that their very basis is riddled with error. In this sense they can be defined as delusional.
Complex psychological interactions are the principal interactions that form human psychology and our understanding of it.
Very complex psychological interactions that involve a method like FIML can eliminate most error, though even FIML cannot remove all of it and even FIML requires years to achieve this end.
Complex psychological interactions (psychological interactions that do not use FIML or something similar) can only reduce error by pretending they are simple interactions (ones involving formal rules).
These interactions “pretend” they are simple for convenience or to avoid ambiguity and argumentation. No person can develop complex psychology without complex psychological interactions.
Since our current understanding of human psychology is based on simple and complex interactions (plus biology), its basis is fundamentally riddled with error and thus delusional.
Human psychological delusion must be removed (by FIML or similar) before we can even begin to understand human psychology. I would go so far as to say that no psychologist can possibly understand or competently treat another human being if they have not practiced complex and very complex psychological interaction for many years.
The lion’s share, if not all, psychological problems (if they are not biological) are caused by the aggregation of error that comes from psychological interactions that fall short of very complex interactions as described above.