All content copyright © 2010-2019 Frank Revelo
Subjective definition: "mental/bodily illness = mental/bodily configuration which results in less happiness than would result from feasible alternative configuration". Subjectively curing mental/bodily illness means modifying mind/body so as to increase happiness. Mental configuration can be translated "belief system" or "pattern of thinking". Qualification "feasible" is to handle bizarre special cases (such as racial discrimination, where a person would be happier if they could be changed to a different race, which is a change to bodily configuration, however their race shouldn't be called an illness).
Objective definition: "mental/bodily illness = behavior/bodily configuration which deviates from society's definition of healthy configuration". Note how "behavior" replaces "mental configuration". Mental configuration is mostly hidden from society (at least with available technologies). Behavior must be used as a proxy.
With respect to the subjective definition of mental illness, it is often true that if the individual is on bad terms with society, happiness will be low. An individual usually gets on bad terms with society by saying or doing things which society disapproves, and this usually happens because the individual thinks things which society disapproves. In other words, thinking in a manner which society disapproves often constitutes mental illness, in and of itself, even by the subjective definition of mental illness. It matters not how this thinking relates to the objective reality of the material world. If society disapproves an idea, then it is madness for the individual to hold the idea, regardless of whether the idea is objectively true or not. The reason is that the impact of society on the happiness of the individual is usually greater than the impact of flawed versus correct ideas with regards to the material world. If society says the earth is flat and threatens to torture anyone who says otherwise, then it is surely madness for the individual to insist that the earth is in fact round, because the reduction in happiness due to accepting that the earth is flat is surely less than the reduction in happiness from being tortured. In other words, the subjective and objective definitions of mental illness may be identical in practice.
Two basic forms of mental illness: (a) too many internal rules leads to depression, due to failure to satisfy bodily desires; (b) too few internal rules leads to prison, lunatic asylum or homelessness, due to conflict between behavior and rules of society. Combination is also possible: too many rules with respect to some behaviors, too few rules with respect to others.
Mind and spirit are synonyms, thus mental illness is the same as spiritual illness. Most bodily illness is actually a symptom of spiritual illness. Spiritual and bodily illness alike are typically Karmic in nature via the process of reincarnation. That is, we bring about our own illnesses by our choices, whether in this life or past lives. Furthermore, our choices in this life will cause health or illness in future lives.