well said miecha. The particular attributes of the four houses are meant to equal one, well rounded individual: Hogwarts. Unfortunately, these attributes aren't just the personality traits of one individual, they are the preferences of the people in the houses; so not so united more warring!

This brings to mind another question: Why is the Sorting Hat necessary if it's up to the preference of the individual student, which house they want to be in? Why can't choosing a house be more like choosing a university. You go on a tour, check out the pros and cons and decide.

Additionally, if the four houses are supposed to equal one united school, why all the secrecy about where the different houses' dorm.s are and all the competion between them ? I mean a bit of 'reward and punishment' discipline is a common classroom management strategy but when and where is the Hogwarts' spirit encouraged not just interhouse competition? This policy and secrecy seems determined to divide the school rather than unite it.