2 - What is mental health?

This is obviously too big a question to discuss here. So the smaller issues I mean here are this kind of thing: Is mental health dependent on the society you're part of? Could you be considered very sane by our Western world and be considered completely unhinged by a tribe of Amazon Indians living two centuries ago? (Ok, trick question). Parallel to this, can you measure sanity by how well you perceive and fit into your society - i.e. the more you fit in and sucessful you are the more mentally healthy you are? Obviously that's the way our society in general perceives mental health - misfits are usually considered at least slightly crazy. This however has the implication that selfish people are very sane, as that's the best way to get ahead in this society (as long as you manage to fake for some people that you're really altruistic). Bur what about extremely selfish people? Surely they're not completely there? (An example used in our debate was the Nazi concentration camp guards). And finally, are there certain actions that would define someone as mentally unhealthy just because they're against our nature (in the biological sense) as human beings, as a species? Feel free to either try and give your own answer or just add more questions!