Each human culture presents its many members with knowledge of reality and with longstanding, adamantly held perceptions that are illusory. For example, unverified cultural transmissions can give rise to widely shared distortions of the world whenever mistaken impressions are consensually validated as if they represent what is real.

In these instances, humans ubiquitously emit culturally biased and scientifically unsupported communications that confuse human reasoning and often promote a certain cortical conceitedness that is not useful in acquiring an understanding of the practical requirements of reality.

Over long time periods, preternatural ideas are passed down from generation to generation, with an unintended result. Distorted perceptions of reality are shared among people, thereby confounding the efforts of humanity to share an adequate awareness of what is real.

When good science emerges, it is initially disturbing because the new science usually challenges well-established but unrealistic ideas about what it means to be human, the "placement" of the human species within the natural order of living things, and the requirements of biophysical reality. New scientific facts of this particular kind are uniformly difficult for people to see because unexpected data expose hubris to view by the human species.

Since humans are shaped early and pervasively by a superabundance of culturally derived transmissions in our perception of reality, it becomes an evolutionary challenge for human beings to see the world as it is and to gain knowledge of the human species as one of many miraculous creatures to inhabit so wondrous a planetary home as Earth.

When a scientist-practitioner of psychology such as myself thinks a patient is suffering from mental illness, that determination is an evidence-based clinical judgment. However, cultural standards of normalcy are not as carefully and rigorously developed as are clinical judgments, but instead are casually agreed upon and promulgated as social norms and conventions that include scientifically validated perceptions of reality as well as misperceptions of what is real.

Because some distorted impressions of the world are valued by those who share them, these misperceptions are readily passed from member to member within a culture, among both peers and the generations.

Deeply disturbed mental patients distort reality so drastically that their incorrect impressions of reality do not become established by being passed along to other people. By contrast, "normal" people in instrumentalities of governance, social organizations and cultures appear not to misperceive reality so sharply, yet distortions of what aggregations of normal people perceive do remain.

A term of art in psychology is useful here, folie a deux. The term means that two people share an identical distortion of reality. This understanding leads to other terms, folie a deux million for a government agency or political party, folie a deux cent million for a social order or folie a deux billion for a culture. These terms refer to misperceived aspects of reality held and commonly shared by many people of a government, a society or a culture.

At least one way to define the highest standard of normalcy for people in these aggregates is in terms of being able to adequately distinguish what is illusory from what is in scientific fact real.