The word itself comes from the root adjective "sane," which stems from Latin "sanus," or "healthy." One could reasonably argue, then, that a sane mind is a healthy mind. Let us examine this further. Health, in general, denotes strength, soundness, proper functioning, especially of biological systems. The mind is generally regarded as the seat of awareness and reasoning, leading us to the conclusion that if one is clear and accurate in his awareness and reasoning, he might be regarded as "sane."
Who shall determine, however, what constitutes clear and accurate awareness and reasoning and what constitutes inaccuracy in these areas? To what degree must errancy intrude into the picture before one is determined no longer sane, but InSane??
There are a number of objective criteria whereby one may observe the workings of a mind and determine their accuracy, but the largest portion of these have been declared to be more useful in determining IntelliGence than sanity. One's ability to perform mathematical computations, identify shapes, take the next deductive step, identify patterns in data, all are related to mental accuracy, but may be poor indicators of sanity. The kinds of tasks which one performs accurately, then, may have an impact on the perception of one as sane or not.
More than mere accuracy has been introduced to the picture, however, as conformance and agreement with societal norms have played as great a role in the determination of sanity historically as any other criteria.
(to be completed as time permits) -- AyeSpy
""SanIty" is variously defined as; the quality of a sound or healthy mind, rationality, the ability to discern right and wrong, "believing and thinking as you ought to believe and think, according to me," and any number of other definitions which users find expedient." Is this even true, or are you only speculating: who defines the term this way? Shouldn't you consider actual attempts to define the term? Shouldn't you at least say something that reflects what psychologists know and believe about sanity and insanity?