Let's start from the beginning, with a layman's explanation of psychology.
A person's mind is composed of subconscious structures of beleifs. This could be termed as it's operating system, as a person's structures do dictate a way a person thinks. Some of these beliefs include "There is a god", "Justice prevails in the end", and "Miracles cannot happen."
More beliefs will arise out of a person's choices in life, which are in turn influenced by previous beliefs. Things like, "I am a terrible mother" or "I will always have my husband" or "That was a worthwhile choice.".
Challenging and replacing these beliefs is the natural state of mental growth of human beings. But this replacement of ideas is a gradual thing, and if too many structures are being tested too quickly, then a person suffers breakdown.
Some beliefs and idea structures are more important than others, and these form the "skeleton" of a person's idea and belief "body". Damage to these ideas may never be repaired, and if healed, that structure will never work as it once did.
Finally, our physical state also influences our mental structures. When one becomes too stressed or exhausted, one may find that their mental structures are lacking, and may grasp at new ideas to justify or keep them going. Ideas such as "I hate Etheopeans", "I am a worthless sack of figs", or "I won't take this anymore; I don't deserve it."
In conclusion, to subtly break someone's sanity, you must systematically attack what they hold dear, exhaust them mentally and physically, and destroy that which they think to be true.
edited 23rd Dec '11 4:59:11 AM by Kraken