If every former Hogwarts student who goes bad was in Slytherin, why has Hogwarts kept the house over the years? Why not disband it?
Not every member of the Slytherin house has gone bad and neither has every bad wizard been in Slytherin.
Here’s a little-known fact that the other three houses don’t bring up much: Merlin was a Slytherin. Yes, Merlin himself, the most famous wizard in history! He learned all he knew in this very house!
Quote from Pottermore, Slytherin Acceptance letter.
Also Draco Malfoy was not bad (in the end), neither was Regulus Black. I could make a list but that's not really the point.
The house would also not be disbanded as it would be disrespectful towards one of the founding fathers of Hogwarts, Salazar Slytherin.
In relation to @Pickett's comment, during the epilogue of The Deathly Hallows when Harry is talking to his son about his son(Albus Severus) possibly being in Slytherin.
“Albus Severus," Harry said quietly, so that nobody but Ginny could hear, and she was tactful enough to pretend to be waving to Rose, who was now on the train, "you were named for two headmasters of Hogwarts. One of them was a Slytherin and he was probably the bravest man I ever knew.”
J.K. Rowling, Harry Potter and the Deathly Hallows - In reference to Snape obviously.
Since the other answers only mention bad non-Slytherins in passing, I'll contribute to the defense of my house with a few examples of evil outside Slytherin (possible spoilers):
Gilderoy Lockhart - Wiped the memories of many incredible people in order to take credit for all their achievements, and thus composed a corpus of lies as his biography. Also a complete coward. Belongs to Ravenclaw House.
Peter "Wormtail" Pettigrew - Betrayed his best friends to Lord Voldemort and became a Death Eater. Revived Voldemort some years after his first downfall. What he lacked in loyalty he made up for in cowardice. Belonged to Gryffindor House.
Quirinus Quirrell - Allowed Voldemort to use his body as a vessel for recovery, sought the Philosopher's Stone, attempted to kill Harry Potter. Belonged to Ravenclaw House.
So disbanding Slytherin House would not end evil. Additionally there's the issue that disbanding a house won't get rid of the wizards. If people are predisposed to evil actions, the absence of a house is hardly going to stop most of them. They would just find somewhere else to commune with their co-conspirators and they'd find a way to do the things they want. Thus it wouldn't be an effective measure anyway.
J.K. Rowling has specifically answered this here. Firstly, as other answerers have pointed out, they're not all bad. In the books, we see the very worst of Slytherin.
But the main point, which seems to be very important to JKR herself, is the key running idea (whether of the founders or the past Headmasters, or something/someone else entirely) that only together can the students be stronger, drawing on their different strengths. Snape and Harry have very different strengths and weaknesses, and neither would have been able to do what they did if they had been members of any of the other houses.
The relevant section is below; I've bolded some of the key points.
Emerson Spartz: Why is Slytherin house still –
J.K.Rowling: Still allowed!
ES: Yes! I mean, it's such a stigma.
JKR: But they're not all bad. They literally are not all bad. [Pause.] Well, the deeper answer, the non-flippant answer, would be that you have to embrace all of a person, you have to take them with their flaws, and everyone's got them. It’s the same way with the student body. If only they could achieve perfect unity, you would have an absolute unstoppable force, and I suppose it's that craving for unity and wholeness that means that they keep that quarter of the school that maybe does not encapsulate the most generous and noble qualities, in the hope, in the very Dumbledore-esque hope that they will achieve union, and they will achieve harmony. Harmony is the word.
ES: Couldn’t —
JKR: Couldn't they just shoot them all? NO, Emerson, they really couldn’t!
ES: Couldn't they just put them into the other three houses, and maybe it wouldn’t be a perfect fit for all of them, but a close enough fit that they would get by and wouldn't be in such a negative environment?
JKR: They could. But you must remember, I have thought about this —
ES: Even their common room is a gloomy dark room—
JKR: Well, I don't know, because I think the Slytherin common room has a spooky beauty.
ES: It's gotta be a bad idea to stick all the Death Eaters' kids together in one place.
[All crack up again ]
JKR: But they're not all — don't think I don't take your point, but — we, the reader, and I as the writer, because I'm leading you all there — you are seeing Slytherin house always from the perspective of Death Eaters' children. They are a small fraction of the total Slytherin population. I'm not saying all the other Slytherins are adorable, but they're certainly not Draco, they're certainly not, you know, Crabbe and Goyle. They're not all like that, that would be too brutal for words, wouldn’t it?
ES: But there aren't a lot of Death Eater children in the other houses, are there?
JKR: You will have people connected with Death Eaters in the other houses, yeah, absolutely.
ES: Just in lesser numbers.
JKR: Probably. I hear you. It is the tradition to have four houses, but in this case, I wanted them to correspond roughly to the four elements. So Gryffindor is fire, Ravenclaw is air, Hufflepuff is earth, and Slytherin is water, hence the fact that their common room is under the lake. So again, it was this idea of harmony and balance, that you had four necessary components and by integrating them you would make a very strong place. But they remain fragmented, as we know.
Slytherin was the house for the ones that can do anything for reach success, or that was what the Sorting Hat told Harry in his first year of Howarts.
The other requirement to enter slytherin is to be a pure blood wizard, but that isn't a bad requirement, if you don't hate the others.
A lot of good magicians come from slytherin: Regulus Black, Severus Snape... Narcisa Malfoy is not bad, and she's from Slytherin too.
You're making the wrong assumption here.
Did they (i.e. the dark wizards) become evil after they joined Slytherin, or where they already evil before that?
The answer would usually be the second one (some people may have been affected by bad influence from their fellow students).
Voldemort was already evil before he joined Slytherin. If Slytherin had been disbanded before he attended Hogwarts, he would have just joined another house, but it (probably) wouldn't have changed much in the end.
Because this is the type of question that only a Slytherin would seriously entertain.
Hufflepuffs aren't about trying to do away with things, they'll take anybody the other houses don't want, and will live and let live. Ravenclaws don't seem to like Slytherin, but from an intellectual point of view we never see anything beyond that. Gryffindors are brave, and how is it brave to want to disband your opponents rather than standing up to them and facing them?
On the other hand, Slytherins are about ambition and blood purity - doing what it takes to get it done. Slytherin himself even broke away from the other three in his own lifetime, even going so far as creating the Chamber of Secrets.
Similar questions can pop up in the minds of naive political activists:
- Left-wing activist: why aren't all right-wing parties banned? They are all evil!
- Right-wing activist: why aren't all left-wing parties banned? They are all evil!
Slytherin is not a crime organization. It's a House. The fact that some people view it as the "House of Evil" doesn't mean that Slytherin is, in itself, evil. Yes, some students from Slytherin might turn out to become evil, but the House itself is not inherently evil. The fact that more students from Slytherin turn out to become evil than from other houses, can be caused by, among other factors, that the most defining characteristic of Slytherin is ambition. Ambitious people have a higher tendency to act, students from other houses can also harbor evil desires, they just lack the ambition to act them out.
Don't forget that the main characters are all from the House which is the greatest rival of Slytherin, and we view the story from their point of view, this might also make Slytherin look more evil than it really is. There were probably many cases where Griffyndor bullies were abusing Slytherin students, but as the main characters weren't the victims in these cases, they don't play a big role in the story.
Let's put all the above issues beside, and take a look at what would happen if they indeed tried to disband Slytherin:
- A lot of Slytherin students come from powerful and respected noble houses. Pissing them off might not be the best idea.
- Students start at Hogwarts at the age of 11, not 7. They already have a much well formed personality than Muggle students starting their first year at 6 or 7. Just dividing them up among the other houses would probably not change their personality very much, and if the four Houses represented temperament, like-minded students would probably find each other and form small cliques anyway.
- If you wanted to entirily avoid students who would have ended up in Slytherin, what would you do? Have a sorting ceremony, and send home all students who got into Slytherin? What would this blatantly prejudicial discrimination accomplish? Refusing education from them would make them uncontrolled hazards to society, now add the feeling of bitterness against all those who rejected them to the already strong superiority complex many Slytherins tend to possess. As a lot of Slytherins come from aristocratic families, they might even found their own school where they would become even more smug in their "special school for the elite".
Why in the world would they disband ANY of the houses of Hogwarts or maybe they should have disbanded all of them. The positive traits that are associated with Slytherin is found in those who are ambitious, can keep their own counsel. Their best traits are cunning, resourcefulness, and ambition. Remember all houses had Voldemort supporters. Peter Pettigrew was a Gryffindor and one of the Maurauders and not only did he betray James and Lily but he helped to bring Voldemort back to human form (sort of).
I understand your question, and unlike some others, don't think it should be dismissed out of hand. After all, on the face of it, it seems a terrible idea to put all the students who are more ambitious and less...well...scrupulous in the same house, as it would seem to create an environment that would bring out the worst in those students. Certainly this is the view taken by Gryffindors like Hagrid when he talked about Slytherin wizards going bad.
However, I'm sure Slytherins probably say the same thing about Gryffindor House. Is putting all the most brave and impetuous students in one group any better (or worse) an idea? Wouldn't that seem to create an environment that would enable reckless behavior? Wouldn't putting all the brainiest kids together encourage aloofness? Wouldn't putting all the most obedient, hardest-working students together in one house foster a lack of critical thinking?
Maybe. The Hogwarts houses have become too insular, and that's something the Sorting Hat goes on about in the later books. However, the original concept, the idea that students of similar character would support each other, act as one another's family-away-from-family, as Professor McGonagall puts it, isn't without merit. If there were no houses, these different types of students would tend to flock together anyway, and the houses' existence gives the students breathing spaces where they can be themselves after class.
So yes, I'd definitely say that the houses should mingle more than they do, but disbanding them, even Slytherin House, doesn't sound like a good plan to me.
It's inevitable that some people will be driven mostly by ambition. It's possible for someone to be ruthless without being simply evil too. We must remember that Hogwarts is for children. They're not yet full adults ready to face the world on their own. Each house is supposed to shape its members.
The existence of Slytherin reflects the reality that darker, driven people exist in the wizarding world and have their place. Consider the character arc of Draco - he does not grow up to become evil. He becomes a friend of Harry, and a moral person in spite of his great ambition and capacity to be ruthless to get what he wants. Why did this happen? At least in part because his school house allowed him to be himself while also exposing him to students from other houses, tempering him.
Put another way, the four house system of Hogwarts prevents each personality type from being isolated and turning inward on itself. Gryffindors are supposed to be "brave" for instance. But as we saw, it's the point of arrogant. It's the place for people who may be brave yes, but see themselves too much as heroes and are resented a bit by others because of it. By forcing them to deal with other kinds of people, their personalities become more well rounded.
Plus don't forget we're dealing with literal magic in this universe. Darker uses of magic exist and must be dealt with. It would be foolish to completely suppress knowledge of aggressive magic at a school, or pretend that some students weren't naturally adept at it. Hogwarts was founded by four wizards trying to find a balance - it would be an interesting story to see them in person, and see how they argued among themselves.
Firstly, your belief that 'every Slytherin student is prejudiced and evil' is wrong. I would not like to repeat the examples of 'good Slytherin' given by others but one example is needed to change your mind.
Merlin was in Slytherin but not much was revealed about him except that he was a great wizard. Pottermore later told us more about him. The wizarding noble prize of sorts, the Order of Merlin, was earlier an organisation started by Merlin. Pottermore itself has no idea of how that organisation became an award but never mind. What was the purpose of it you ask?
It was the first institution to advocate for Muggle-born equality. Started by a Slytherin. Doesn't sound right to you?
Merlin was the first wizard in recorded history to ever think of Mudbloods as equals to wizards and actually campaign for their rights. This is the reason why he is regarded as a great wizard. The colour of the First Order of Merlin (reward, not organisation) is green to signify Merlin's house.
Slytherin is regarded as the supremacist house but what more evidence should you want other than the above text that it is not?
We think that Salazar Slytherin was a racist as he refused to teach Mudbloods but the circumstances might have forced him to make that statement. It was after all a time when people thought of wizards and witches as Satanic, so he might have feared that Mudbloods might still be loyal to their anti-magic beliefs and Hogwarts, which was at that time a safe haven for wizarding children, might have been exposed to Puritan eyes.
Salazae Slytherin definitely tried to ensure that Hogwarts was wiped out off Mudbloods in the future through his Basilisk and that was quite evil but that might have also been just because he feared the same fate for Hogwarts in the future of being exposed by Mudblooods.
It is also possible that Slytherin started the ideas of blood supremacy through these fears, not that he was following them when he showed his hate for Mudbloods. Because it is evident that Muggles and wizards lived together quite harmoniously in the past from the many tales such as of Linfred Potter of Stinchcombe, Harry's ancestor. Wizards only marrying wizards might have been a laughable idea at those times.
Thus, the snake's house is actually not all prejudiced and evil.
It is also notable to tell that you see the Slytherin house through the eyes of Harry Potter and his friends, who intensely hate Slytherin and also at a time when a war has just ended and a new one is just starting where the antagonist was a Slytherin.
Rowling herself through Pottermore has told us that the views of the main characters are not completely unbiased and has many articles on how Slytherin isn't evil.
Most of the Slytherins that the characters encounter are bad in a way or the other but that doesn't deem all Slytherins evil. It has produced many a great wizard and its motto itself is greatness. Even Dumbledore was a blood supremacist in his teens, but he turned out a great chap later on, similar to Snape or Malfoy. So shouldn't Gryffindor also be banned? (I can hear you gasp in disbelief as you read this line :))
Hope I answered your question and you get the point.