http://en.wikipedia.org/wiki/Multiple_personality_disorder Multiple Personality Disorder is basically a subconscious shift into another alter ego and the alter ego gives itself a name and identity. There are some people who have more than 60 alter ego's and they can't control the random shift of these random aliases. One minute you're like a 3 year old sucking your thumb, the next minute you're like an ill mannered, illiterate teenager and the next minute you're an old person etc. Each distinct personality has its own pattern of perceiving and interacting with the environment. The question is, basically, doesn't this disorder infringe upon and negate the concept of freewill? Another interesting question is, why did God create such a disorder as this, for what purpose?