The world of Harry Potter holds that the Sorting Hat sorts a child based on what traits they possess. The brave go to Gryffindor, the intellectual to Ravenclaw, the cunning to Slytherin and the hardworking to Hufflepuff (or, if you believe the Sorting Hat in The Prisoner of Azkaban, Hufflepuff just gets the leftovers). However, as I was rereading the series, I came across a lot of holes in that line of thinking.
First of all, many of the kids sorted don’t actually have the traits espoused by their heads. 11-year-old Neville isn’t brave at all; he’s even scared of his own shadow. 11-year-old Draco isn’t anywhere near cunning (basically alienating Harry Potter, the wizarding world’s biggest celebrity). And don’t get me started on Crabbe and Goyle.
Now Neville definitely becomes brave, and you could argue that Draco develops cunning down the line. But the point is, they didn’t have those traits the moment they were sorted. So perhaps the Sorting Hat can somehow predict their future? Or read into their minds to see which traits they’ll develop if nurtured. That’s certainly possible, but how can you possibly tell which traits an 11-year-old will have? They’re basically the age of a 5th grader. And let’s assume, for the sake of argument, that in the wizarding world personalities are somehow fixed at the age of 11 (unlike in the real world). Then shouldn’t the data the Sorting Hat collects be extraordinarily valuable to help ensure your students grow up to be healthy individuals? You wouldn’t use it to assign a student their dormitory and then never touch that info again.
And that’s clearly also not true. Peter Pettigrew was sorted into Gryffindor and he never became brave. In fact his character is literately defined by its cowardice. Similarly, Marcus Flint gets held back a year. What’s cunning about that?
And that’s not even addressing the biggest issue with the above theory (and the biggest thing in favor of my alternate explanation): students’ choice matters. Probably the biggest insight into how the Sorting Hat works is what Harry tells his son Albus – “The Sorting Hat takes your choice into account.”
And we see this not only with Harry (who chose Gryffindor over Slytherin) but also I’d wager Hermione (who chose Gryffindor over Ravenclaw), as well as anyone who’s family traditionally gets sorted into a house. It’s hard to imagine every single Weasley being a Gryffindor or every single Malfoy a Slytherin, if your choice was determined by your personality (and not your choice).
So clearly there’s an issue with the standard idea of how the Sorting Hat sorts. But then, if it doesn’t sort based on inner traits, how does it decide who goes where? I’d argue is sorts a child based on their values. Specifically, a child who believes Bravery and Courage are the most important traits would go to Gryffindor, where as a child who values Intellectualism and Love of Learning above all else would go to Ravenclaw. The key difference is that a child need not possess that trait, but mere value it.
This explains how Draco, completely inept at becoming cunning (but growing up in a family where it is prized), can be sorted into Slytherin while Hermione (who is an intellectual, but wishes to become like her heroes in Gryffindor) can choose to become a Gryffindor. Additionally, this neatly explains how polarized the houses are towards one another. If you take all the kids that value bravery and stick them into one house (an environment where everyone else also values bravery above all else), you’ll start to see them all become brave (and, in some cases, to the exclusion of the other traits).
If this theory is true, it also shows how badly the house system needs to be revamped (to stress inter-house friendships and development of all 4 major traits). But that’s a whole ‘nother discussion.