>>1469555While I'm critical of how the term mental illness is used today I still think you're retarded.
Most people operate within a certain scope of relatively similar mental/behavioural patterns. They feel the same emotions, they react the same way to specific stimuli, and their decision making priorities follow somewhat similar rationales. That's not to say all people are the same - not two people on earth will ever have the exact same collection of traits, experiences and abilities that make up their personality and being.
Most people have some kind of quirks, that make them behave or think in ways that might be considered abnormal, without affecting their ability to function in society. But for certain people, these deviations from normal behavioural patterns can be dangerous or detrimental to the point that they're considered behavioural disorders. Sometimes, this is due to biological reasons, like brain trauma, but often they are entirely psychological in nature. What would you describe this as, if not a mental illness?