Sanity (from Latin: sānitās) refers to the soundness, rationality and healthiness of the human mind, as opposed to insanity. A person is sane if he/she is rational. In modern society, the terms have become exclusively synonymous with compos mentis (Latin: compos, having mastery of, and mentis, mind), in contrast with non compos mentis, or insane, meaning troubled conscience.
Psychiatry and psychology 
A theory of sanity was proposed by Alfred Korzybski in his general semantics. He believed that sanity was tied to the structural fit or lack what is actually going on in the world. He imposed this notion in a map-territory analogy: "A map is not the territory it represents, but, if correct, it has a "similar structure" to the territory, which accounts for its usefulness." Given that science continually seeks to adjust its theories structurally to fit the facts, i.e., adjusts its maps to fit the territory, and thus advances more rapidly than any other field, he believed that the key to understanding sanity would be found in the study of the methods of science (and the study of structure as revealed by science). The adoption of a scientific outlook and attitude of continual adjustment by the individual toward his or her assumptions was the way, so he claimed. In other words, there were "factors of sanity to be found in the physico-mathematical methods of science."
In The Sane Society, published in 1955, psychologist Erich Fromm proposed that, not just individuals, but entire societies "may be lacking in sanity". Fromm argued that one of the most deceptive features of social life involves "consensual validation.":
|“||It is naively assumed that the fact that the majority of people share certain ideas or feelings proves the validity of these ideas and feelings. Nothing is further from the truth... Just as there is a folie à deux there is a folie à millions. The fact that millions of people share the same vices does not make these vices virtues, the fact that they share so many errors does not make the errors to be truths, and the fact that millions of people share the same form of mental pathology does not make these people sane.||”|
In criminal and mental health law, sanity is a legal term denoting that an individual is of sound mind and therefore can bear legal responsibility for his or her actions. The official legal term is compos mentis. It is generally defined in terms of the absence of insanity (non compos mentis). It is not a medical term, although the opinions of medical experts are often important in making a legal decision as to whether someone is sane or insane. It is also not the same concept as mental illness. One can be acting under profound mental illness and yet be sane, and one can also be ruled insane without an underlying mental illness.
Legal definitions of sanity have been little explored by science and medicine, as the concentration has been on illness.
See also 
|Look up sane or sanity in Wiktionary, the free dictionary.|
||This article needs additional citations for verification. (December 2010)|
- Science and Sanity by Alfred Korzybski
- When Ecology Does Not Count: Checking the Ecology of The Ecology Check by L. Michael Hall, Ph.D.
- Consensual validation at vault-co.com[dead link]
- Fromm, Erich. The Sane Society, Routledge, 1955, pp.14–15.