What Jo says about...
"The Rules" of Harry Potter's Wizarding World

Please note: unless you see quotemarks, these are summaries, and not JKR's words themselves. Please see the linked article for the actual text.

• JKR: "To invent this wizard world, I've learned a ridiculous amount about alchemy. Perhaps much of it I'll never use in the books, but I have to know in detail what magic can and cannot do in order to set the parameters and establish the stories' internal logic." [Read the exact quote from The Herald, 1998]
• Difference between charms and transfiguration? JKR: "With a charm you add properties to something. With a transfiguration you change its nature completely; the molecular structure alters..." [Read the exact quote from The Herald, 1998]
• JKR: "I spent a lot of time inventing the rules for the magical world so that I knew the limits of magic. Then I had to invent the different ways wizards could accomplish certain things." [Read the exact quote from Barnes & Noble chat #1, 1999]
• Nobody knows where magic comes from – sometimes it is inherited, sometimes only one person in a family has it. [Read the exact quote from Barnes & Noble chat #1, 1999]
• There is a character who, in desperate circumstances, manages to do magic quite late in life. This is very rare. [Read the exact quote from Barnes & Noble chat #1, 1999]
• One of the rules she has for her books is that "Magic cannot bring dead people back to life…. Once you’re dead, you’re dead." [Read the exact quote from WBUR interview, 1999]
• JKR: "In my world wizards come of age at 17 - age 17. So in book 7 you'll see Harry come of age, which means he's allowed to use magic outside school, and you'll see the end of that school year." [Read the exact quote from the Diane Rehm Show interview, 1999]
• The happiest people don’t become ghosts. [Read the exact quote from Scholastic chat #1, 2000]
• No magic power can resurrect a truly dead person. [Read the exact quote from The Guardian Unlimited, 2000]
• Wizards need money because "there is legislation about what you can conjure and what you can't. Something that you conjure out of thin air will not last." [Read the exact quote from the South West News Service interview, 2000]
• "The five years I spent on HP and the Philosopher's Stone were spent constructing The Rules. I had to lay down all my parameters. The most important thing to decide when you're creating a fantasy world is what the characters CAN'T do." [Read the exact quote from the South West News Service interview, 2000]
• Witches and wizards don’t have to go muggle school before Hogwarts. [Read the exact quote from the Scholastic chat #2, 2000]
• Goblins manage to get muggle money back into circulation after muggles have changed it into wizard money at Gringotts. (They are like "Fences" [British & American slang]). [Read the exact quote from the AOL chat, 2000]
• The animal one turns into as an animagus reflects your personality. [Read the exact quote from the AOL chat, 2000]
• On the theme of tolerance in the books: "One way to learn tolerance is to take the time to really understand other people's motives. Yes, you're right. Harry is often given an erroneous first impression of someone and he has to learn to look beneath the surface. When you look beneath the surface he has sometimes found that he is being fooled by people. And on other occasions he has found very nice surprises." [CBC-00b]
• Dementors don’t breed, but grow like fungus where there is decay. [Read the exact quote from The Canadian Press, 2000]
• You can’t domesticate a dragon! [Read the exact quote from the Raincoast Books interview, 2001]
• Wizards don’t need the internet; they have something more fun to find out what goes on in the outside world. [Read the exact quote from the Raincoast Books interview, 2001]
• Fluffy is roaming the Forbidden Forest, since "anything that is dangerous is released to the forest." [Read the exact quote from the BBC Blue Peter interview, 2001]
• You can do unfocused and uncontrolled magic without a wand, but to do really good magic you need a wand. [Read the exact quote from BBC Red Nose Day chat, 2001]
• A Galleon is approximately five pounds [British money], but the exchange rate varies! [Read the exact quote from BBC Red Nose Day chat, 2001]
• JKR: "I’ve used bits of what people used to believe worked magically just to add a certain flavor, but I’ve always twisted them to suit my own ends. I mean, I’ve taken liberties with folklore, um, to suit my plot." [Read the exact quote from "Harry Potter and Me," 2001]
• "I loathe books that have inconsistencies and leave questions unanswered. Loopholes bug the h**l out of me ... so I try to be meticulous and make sure that everything operates according to laws, however odd, so that everyone understands exactly how and why." [Read the exact quote from the Sydney Morning Herald, 2001]
• The Harry books are supposed to be full of surprises, but Jo tries to makes sure things unfold in a realistic way. [Read the exact quote from the Sydney Morning Herald, 2001]
• Dumbledore speaks for JKR. [Read the exact quote from the Chamber of Secrets DVD, 2003]
• If JKR needs to tell the readers something, she lets Hermione or Dumbledore say it. [Read the exact quote from the Chamber of Secrets DVD, 2003]
• Arithmancy is "predicting the future with numbers." [Read the exact quote from Royal Albert Hall, 2003]
• To see the Thestrals, the death that you have witnessed has to have "sunk in." One of the reasons for this is that JK didn’t want to have to introduce them at the end of GOF and not explain them. [Read the exact quote from Royal Albert Hall, 2003]
• 12 is the maximum number of O.W.L.s you can receive. [Read the exact quote from World Book Day, 2004]
• Before Hogwarts, wizard children can go to muggle school or be educated at home. The Weasleys were taught by Mrs. Weasley. [Read the exact quote from World Book Day, 2004]
• If a muggle saw Hogwarts, they would just see an old ruin with a sign "keep out, dangerous building." [Read the exact quote from World Book Day, 2004]
• Special messengers are sent to muggle parents to explain about Hogwarts when their child turns 11. [Read the exact quote from World Book Day, 2004]
• Can we believe everything the sorting hat says? JKR: "The sorting hat is certainly sincere." [Read the exact quote from World Book Day, 2004]
• House-elves have "powers wizards haven't got (but wizards have also got powers that house-elves haven't)." [Read the exact quote from World Book Day, 2004]
• The Muggle and Magical worlds will never be rejoined. [Read the exact quote from World Book Day, 2004]
• JKR: "Most of the spells are invented, but some of them have a basis in what people used to believe worked. We owe a lot of our scientific knowledge to the alchemists!" [Read the exact quote from an Amazon.com interview, undated]
• To people like Lucius Malfoy, a Muggle-born is as bad as a Muggle, so Harry is considered Half-Blood because of his mother's parents. In effect, a Muggle Grandparent "pollutes" the blood. (Read the rest of JK's response here to see how this relates to the Nazi's attitude to Jews.) [Read the exact quote from Jo's website]
• "Information you take directly from [JKR's website] will be truthful and accurate (I might occasionally joke, but as time goes on, you'll learn to tell when I'm joking). Do not trust anybody else claiming to have found information on this site that you cannot access, however seemingly convincing the images they provide to support their story." [Read the exact quote from Jo's website]
• Wizards can make themselves untraceable, which is why they can't be found simply by sending and following owls. [Read the exact quote from Jo's website]
• Prefects can take points — Ron got it wrong on OotP. [Read the exact quote from Jo's website]
• Wizard portraits are not living or thinking entities, they are only a "distillation" of the real person. This "aura" can give advice or repeat catchphrases but not much more. [Read the exact quote from Edinburgh Book Festival, 2004]
• Ghosts can communicate more effectively with people than the portraits. [Read the exact quote from Edinburgh Book Festival, 2004]
• Ghosts were people who were very afraid of death. [Read the exact quote from Edinburgh Book Festival, 2004]
• Muggle-born wizards were not allowed to be Death Eaters. [Read the exact quote from Edinburgh Book Festival, 2004]
• In CoS, Colin Creavey's muggle camera worked because it was "running off the magical atmosphere" and developed in a magical potion. [Read the exact quote from Jo's website]
• JKR: "Peeves isn't a ghost; he was never a living person. He is an indestructible spirit of chaos, and solid enough to unscrew chandeliers, throw walking sticks and, yes, chew gum." [Read the exact quote from Jo's website]
• The Order do not communicate with chocolate frog cards, or any object that would have to be carried on and remembered by the person. They use a form of communication that needs only a wand, and we have already seen it used by an order member before we even knew the order existed. [Read the exact quote from Jo's website]
• JKR wrote the information found on the Wizard Cards; however some of the spells used in the movies (Lacarnum Inflamari) were made up by Steve Kloves. [Read the exact quote from Jo's website]
• No book character has returned from the future. [Read the exact quote from Jo's website]
• Veritaserum is not used in criminal trials because it works best on "‘the unsuspecting, the vulnerable and those insufficiently skilled (in one way or another) to protect themselves against it." Veritaserum is not infallible. [Read the exact quote from Jo's website]
• Wizards have ways of making sure their voices are heard from beyond the grave. [Read the exact quote from Jo's website]
• Most wizard children are home educated before Hogwarts because they cannot be trusted to keep their magical abilities hidden from muggle schoolmates. [Read the exact quote from Jo's website]
• The plural of Patronus is Patronuses (not Patroni). [FAQ Poll answer 15 July 2005]
• The Sorting Hat has never been wrong. When it talks on its own it comes from "the founders themselves." [Read the whole quote from the Leaky Cauldron, 2005]
• Jo thinks that there are about 3,000 wizards in Britain, though she admits that being specific about numbers is not "how I think." [Read the whole quote from the Leaky Cauldron, 2005]
• Pensieves "recreate" the entire reality of the memory and are free of any personal interpretations or biases. Even things not initially noticed are recorded. [Read the entire quote from the Leaky Cauldron, 2005]
• Not everyone in Slytherin house is hateful. The house is important to Hogwarts to create balance. [Read the entire quote from the Leaky Cauldron, 2005]
• The four houses “correspond roughly to the four elements.” Gryffindor is fire, Ravenclaw is air, Hufflepuff is earth, and Slytherin is water. [Read the entire quote from the Leaky Cauldron, 2005]
• Witches and wizards can Disapparate when they’re in danger and they can’t/won’t stay and fight. [Read the entire quote from the Leaky Cauldron, 2005]
• Glasses do not protect one from a Basilisk. Cameras do because there are mirrors and numerous lenses. [Read the whole quote from ITV, 2005]
• You do not know what animagus form you will take until you have transformed. [Read the whole quote from ITV, 2005]
• Harry is not a Metamorphagus; he is just a boy who was "clearly magical from birth." Incidents like him growing his hair back were due to his untrained, uncontrolled magical powers bursting out when he was angry or frightened. [Read the exact quote from Jo's website]
• Harry discovers that Muggle world problems take an even more extravagant form in the Wizarding World because everything is exacerbated by magic. "Human nature is human nature, whatever special powers and talents you have." [Read the whole quote from R&J, 2006]
• Muggles cannot brew potions because there is always a magical component, and at some point you would have to use a wand. [Read the whole quote from RCMH1, 2006]
• If a muggle picked up a wand something accidental and possibly quite violent would be likely to occur. The wand is a vessel for what lies inside a person. You need the magical ability to make it work properly. [Read the whole quote from RCMH1, 2006]
• We will learn more about the relationship between wands and their wizards/witches in book 7. [Read the whole quote from RCMH1, 2006]
• Wandmakers can choose wand cores “that are particular to their country.” Ollivander was given her three favourite cores from the many she had written down. [Read the whole quote from RCMH1, 2006]