What is an illness? An illness is a type of condition. What is a condition? A condition is a “color reality“. What is a color reality? A color reality is something you can experience but cannot intelligibly talk about to a person who has never experienced the thing for themself. For example, if you tell a totally color blind person (see image 1 below) that your car is red, they CANNOT understand you. Words that convey color realities, like the word “red,” are called “color-real words.”
Now, what is a mental illness? A mental illness is a brain illness or a hypothozic illness. A hypothozic illness is an UNPROVEN illness of the brain MERELY believed to be indicated by one or more uncommon mental experiences. Note that the term “mental illness” refers to both proven and unproven things. Proven-things mental illness is treated with physical cures and unproven-things mental illness is treated with psychogenic (“not physical”) cures. Proven-things mental illness is a brain disease. Unproven-things mental illness is NOT a brain disease.
Now, what are the symptoms (signs) of mental illness? The symptoms of mental illness are psycho-internally (that is, within a person) unstoppable (by the person with the symptoms) harm to oneself and/or psycho-internally (that is, within a person) unstoppable (by the person with the symptoms) harm to one or more people other than oneself.