You do not.

Sanity is measured by the coherencecy of our natural experience and the simplicity by which it demonstrates that. The simplest measure of insanity is psychosis and so sanity is alignment of experience with the concepts of its objects.

There are always differing opinions in existence. You have yours, I have mine. Which are correct, which are false? The real answer is that they’re all correct AND incorrect at the same time, because everyone is subject to their own personal experiences and points of view.

From an existential understanding (perhaps spiritual), the universe manifests in all forms, in all times, in all spaces, simply to experience existence as throughly as possible to exhaust all possibilities through various combinations and permutations. If one could equate this to “God” or some manifestation of the divine reality, then regardless of bias, they are all necessary for existence.

So, it’s very simple. Whether someone is right or wrong holds no meaning, only that you accept it, because whether or not you agree, it still exists and therefore is fundamental to the entirety of existence.

At least, that’s my opinion. You may think or believe differently, and that’s okay.

I don’t.

I take it for what I consider it to be: a variable mix between a social contract (people agreeing on what is right and wrong (edit: healthy/not healthy), like with every single other thing going on in any society, whether I agree or not with them is not the point) and some common sense (what it means to be healthy (what sanity is referring to as far as I know) without arguing about abstract notions, like one would try to explain it to a young child maybe?)

So, really for me it’s an ad-hoc definition that has changed many times already, and will change again but it’s also something obvious that I would describe as being able to live among other people not in a perpetual state of anxiety… which may also incidentally imply I would not qualify as the best example of a sane person, who knows?