The wizarding world created by J.K. Rowling for the Harry Potter books isn't like, say, J.R.R. Tolkien's Middle Earth. Where Tolkien had created his elaborate world long before he even had the idea for The Hobbit, Rowling's wizarding world was less an exercise in world-building and mainly just meant as a fun setting for her story. This is a perfectly valid method of worldbuilding, and in the context of whimsical children's books, it works extremely well. Of course, Rowling has been all too happy trying to please fans who want this setting to be a massive Middle Earth-style mythology, constantly expanding the universe through Pottermore, the Fantastic Beasts movies, and various tidbits in interviews and on Twitter. When taken so seriously, the seams in the world-building show more and more. Even the biggest fans got to admit, a lot of the wizarding world doesn't make much sense under scrutiny.
Whether or not this nonsense is a bad thing or not depends a lot on context. A lot can be forgiven by a fun tone and top-notch storytelling, so a lot of plot holes and illogical elements are easily ignorable when simply enjoying the original books and movies. In some cases the nonsensicality actually adds to the charm; it wouldn't be fun if all the characters acted perfectly rational all the time. It's in the expanded universe stuff, where attempts to explain these sorts of things only make them more confusing, where Rowling's wizarding world becomes subject of harsher critique. This list goes through 20 things about the wizarding world that, whether due to inconsistency or its convoluted nature, will make even the most hardcore Potterheads roll their eyes.
20 WHY NO WIZARD COLLEGES?
Hogwarts' extremely lopsided education only becomes worse when you realize that there's no higher education for wizards. Why isn't there? Based on an interview hosted by Scholastic on February 3, 2000, it sounds like Rowling didn't want there to be a University for Wizards so she wouldn't have to write about it.
Students have to decide on a career in their final years at Hogwarts. If necessary, they'll get additional training and apprenticeship for their specific career interests. Kind of a bummer for any indecisive witches and wizards hoping to further explore their options and go the Liberal Arts route.
19 WHY IS THERE AN "EVIL" HOUSE?
OK, we get it, Slytherin isn't "evil" by necessity. The Slytherin traits of cunning and ambition aren't bad ones to have. So why is it that in the books, the house churns out a student body that's almost entirely on the Death Eaters' side? Even the Slytherins who get some degree of redemption are still bullies (Draco Malfoy,) sleazebags (Horace Slughorn,) and vindictive creeps (Severus Snape).
The Cursed Child play does make an effort to present more well-rounded decent Slytherins, but you can't escape that in the original series, Rowling basically reduced Slytherin to "the evil house." Why would any school with any sense, especially one supposedly dedicated to being welcoming and inclusive, let such a house thrive?
18 IGNORANCE OF MUGGLE TECHNOLOGY
You can generally understand why wizards reject the use of muggle technology. Wizards don't need a lot of muggle technology, and because of the Statute of Secrecy, their society is closed off from the muggle world. Rowling's also explained that a lot of technology goes haywire around magic.
That said, the complete ignorance in the wizarding world about how things even work is baffling. If the majority of wizards are half-bloods and a good chunk are muggle-born, then there's no logical excuse for the pure-blood minority, especially a supposed "Muggle Artifacts" expert like Arthur Weasley, to not even know what a rubber duck is!
17 ...EVEN PLUMBING
Hogwarts might have bathrooms now, but it didn't until the 1800s. A Pottermore article on the history of the Chamber of Secrets says "this was a rare instance of wizards copying Muggles, because hitherto they simply relieved themselves wherever they stood, and vanished the evidence."
Uh-huh. This factoid has become a huge joke in the Harry Potter fandom, as an example of Rowling both thinking too hard and not hard enough about random aspects of the wizarding world. This raises so many questions. If this worked, why change to plumbing? How would underage wizards "vanish" their evidence if they're can't use magic outside school? If the Greeks, Romans, Persians, Indians, and Chinese had plumbing thousands of years ago, are we to believe all wizards didn't?
16 HAGRID'S IMPROBABLE BIRTH
We're not going to argue with the genetic possibility of human and giant DNA mixing to produce offspring, because giants are fictional and why not? What we can argue about are the physical... "mechanics" of producing such offspring. An English Mastiff and a teacup dog are genetically compatible for making offspring, but when it comes to the logistical aspects, well, that's a challenge...
For scale purposes, Hagrid's full-giant half-brother Grawp is 16 feet tall and considered tiny by giant standards. We're not saying it'd be impossible for Hagrid's human father to mate with his giant mother, but we just don't want to think about how that possibly works.
15 WATCHING THE TRIWIZARD TOURNAMENT
The three tests of the Twiwizard Tournament in Goblet of Fire are full of blood-curdling excitement... if you're participating. For the spectators, the first task with the dragons would be awesome to watch, and based on the seating layout you could probably make out the challenges in the maze in the third task.
The second task, with the mermaids? All the spectators are just watching the surface of a lake for an hour with no idea what's happening below. One must imagine all the students in the crowd are just taking a nap while it's happening, just happy to be excused from classes.
14 WHY CAN'T YOU TRANSFIGURE FOOD?
One of the big struggles in the long camping section of Deathly Hallows is acquiring food. Hermione makes it clear that you can't create food through transfiguration, that being one of the five Principle Exceptions to Gamp's Law of Transfiguration. This might make sense if animal transfiguration wasn't a thing.
In the first book, Professor McGonagall transfigures her desk into a pig. If you can turn a desk into a pig, why can't you make that pig into bacon? You can come up with your own theories of how these laws work. Maybe the bacon would taste like a desk, or maybe the transformation doesn't last long enough to digest nutrition. Or maybe it's just a silly plot contrivance you shouldn't think too deeply about.
13 HOW OLD IS MCGONAGALL?
Until Fantastic Beasts: The Crimes of Grindelwald came out, we knew Professor Minerva McGonagall's age. She was born in 1935 and, according to Order of the Phoenix, started teaching at Hogwarts in 1956. Somehow, this canon went out the window with Crimes of Grindelwald, with McGonagall appearing as a professor in a scene set in 1937.
You can't pass this scene off as being a relative, as the published screenplay specifies it's Minerva McGonagall in the scene. Either Rowling forgot her own continuity, McGonagall has some nonsense reason to lie about her age in the main series, or there's some convoluted Time-Turner shenanigans going on.
12 "BLOOD OATHS" ARE MEANINGLESS
Be warned, there are going to be a lot of Crimes of Grindelwald complaints on this list. The recent film is by far the worst-reviewed aspect of Potter canon in part because so many aspects of its plot make little sense. One such aspect is the "blood oath" between Grindelwald and Dumbledore.
The blood oath is Dumbledore's excuse for not fighting Grindelwald. The problem is that, unlike an Unbreakable Vow, we know this blood oath can't be permanent because we know Dumbledore does eventually fight Grindelwald. What's the point of this obviously breakable oath? It just seems like an excuse for the movie to dodge the more logical subtext of Dumbledore's reluctance to fight Grindelwald: his discomfort battling his ex-boyfriend.
11 DOES ACCIO WORK ON ANIMALS OR NOT?
In the Harry Potter books, it does seem like Accio, the Summoning Charm, works on living beings. Harry practices Accio on a toad in Order of the Phoenix, and Ted Tonks and Dean Accio salmon in Deathly Hallows. When asked why Newt Scamander didn't just Accio his beasts in the first Fantastic Beasts movie, however, Rowling seemingly changed the rules, claiming you can't directly Accio animals.
Rowling would then break this rule again in Crimes of Grindelwald, where Newt flat-out Accios a Niffler. Maybe you could say it works on smaller animals and not on larger animals based off the examples we've seen, or you could say Rowling just can't make up her mind.
10 APPARITION AT HOGWARTS: ALLOWED OR NOT?
In the books, apparition is blocked off at Hogwarts to all wizards (house elves can apparate short distances within the castle). While the anti-apparition charm is shown to be temporarily liftable for necessary classes, in general, the safety precaution stands. So why do people freely apparate onto the Hogwarts grounds in Crimes of Grindelwald?
According to the "Hogwarts Express" article on Pottermore, the anti-apparition charm was already in place before the International Statute of Secrecy in 1692, so it's not a recent invention. You could maybe explain that it was lifted for some reason in the 1920s, but we need a good reason why such a logical safety measure was temporarily abandoned.
9 DO WIZARDS HAVE DENTISTS?
This is a problem with the movies rather than the books. In the books, the answer to this question is pretty clear: wizards don't need dentists when magical healers can treat the teeth as well as the rest of the body. In the movies, it's confusing. The first movie includes a dentistry sign in Diagon Alley and the second movie lists "dentist" as a location on the Weasleys' location-tracking clock.
In the Half-Blood Prince movie, however, Professor Slughorn doesn't know what Hermione's talking about when she mentions her parents are dentists. Has Slughorn been living under a rock or did David Yates have a radically different vision of the wizarding world's relationship to dental hygiene than Chris Columbus did?
8 WHAT ABOUT MATH AND ENGLISH CLASSES?
Hogwarts students aren't completely ignorant of non-magical matters, typically being home-schooled for elementary education, but they're still woefully uneducated in regards to them. All the required courses are focused on magic. Arithmancy is the only math-related elective, and Study of Ancient Runes is the only thing remotely resembling a language or classical literature course.
This would basically be like if a muggle high school taught almost all science courses, with a couple social studies courses, without any math or English requirements. That'd be ridiculous. Honestly, wouldn't knowing advanced math actually help with practicing magic, the same way you need advanced math for complex science?
7 HUNTING UNICORNS IS Villainous... BUT NEEDED FOR POTIONS?
It's established in one of the most frightening scenes in Sorcerer's Stone: hurting a unicorn is such a grave sin that the moment the creature's blood touches your lips you are cursed forever. If you're not Lord Voldemort pursuing immortality at all costs, it doesn't seem worth it... so who's collecting the horns that all first year Hogwarts students need for their potions classes?
The dubiously canonical Game Boy Advance game attempts to give an explanation of how this works, claiming unicorns occasionally shed their horns. Even so, that same game says such shedding is a rare occurrence, so we don't trust that the Diagon Alley apothecaries got all their unicorn horns from humane suppliers.
6 THE ECONOMICS OF PARCHMENT
The wizarding world's economics don't make a ton of sense in general. J.K. Rowling freely admits it's not her strong suit. One aspect that's particularly surprising if you stop to think about it is just how expensive it is for Hogwarts students to do their homework. We're not talking about the cost of magical supplies. We're talking about parchment.
Parchment was historically far more expensive than paper. Assuming homework plus notes equals about 300 sheets per student per year, that's more than the cost of skinning of a whole flock of sheep (yeah, parchment ain't vegan either). English switched from parchment to paper over a century before the Statue of Secrecy so wizards have no excuse holding to for such pricey outmoded technology.
5 "THE TRACE" DOESN'T SEEM TO WORK
The Trace is one of those pieces of magic which seemingly runs on what's most dramatic to the plot rather than on any apparent consistent rules. Placed on all underage wizards, it allows the Ministry to track if kids are illegally using magic outside of Hogwarts. What it actually traces is if they're in the vicinity of magic, which makes it effectively useless on kids with wizard families and only meaningful for those in the muggle world.
Sometimes, it doesn't even work with that. When Tom Riddle Avada Kedavra'd his muggle father and grandparents at the age of 16, somehow the Ministry received no alert. Did Riddle find some way to block The Trace or did it stop working for some other reason?
4 EVERYTHING OUTSIDE OF THE UNITED KINGDOM
The basic rule of J.K. Rowling's world-building is that the further away she gets from the United Kingdom, the less her wizarding world makes sense. This wasn't an issue in the main Harry Potter series, which is set entirely in the UK, but her attempts to expand the universe on Pottermore and in the Fantastic Beasts movies strain believability.
The "Magic in America" history on Pottermore was rightfully criticized for its uncomfortable handing of Native American spirituality. Even details that aren't insensitive are still baffling. Are we to believe that every wizard in America attends the same school? Details about other countries show a lack of imagination; where England gets "Hogwarts," Japan's wizarding school is just "Mahoutokoro," which literally translates to "magic place."
3 HOGWARTS IS AWFUL
Look, we know every kid who read the Harry Potter books hoped to find a letter to Hogwarts on their 11th birthday. Hogwarts is exciting and magical and cool. It's also a place which, if taken the least bit seriously outside of the context of a whimsical children's story, would be an absolutely horrifying nightmare of a school in need of shutting down immediately.
Most of the faculty are malicious, incompetent, or both. The cafeteria's run on elf labor. The grounds themselves, with that destructive whomping willow and dangerous beasts roaming the Forbidden Forest, are a lawsuit waiting to happen. Students regularly don't survive their time at Hogwarts. And this is a place the survivors were happy to send their kids to?
2 FRED AND GEORGE KNEW ABOUT PETTIGREW
The revelation that the Weasleys' family rat Scabbers was actually the Death Eater Peter Pettigrew was a shocker to almost everyone. Everyone, that is, except for Fred and George. They had the Marauder's Map and therefore they knew Peter Pettigrew was around before everyone else.
They might not have known who Pettigrew was, but they would certainly know that there was some strange man sleeping with their little brother Ron every night if they ever looked at the Gryffindor common room. J.K. Rowling tried to argue on her old website that they didn't notice, but we don't buy that, nor do Fred and George's actors who've joked about this plot hole.
1 VOLDEMORT NEVER STEALS HARRY'S GLASSES
Think about it for a second. Ignore the fact it's kind of weird that wizards need glasses anyway to begin with, with all their magic healing abilities. The easiest way for Voldemort to beat Harry in any duel would be to yell "Accio glasses" and temporarily blind his bespectacled opponent.
Why doesn't He Who Must Not Be Named ever try pulling this surely effective trick? It's minor as oversights go, and certainly far from the most distracting or bothersome of the various plot holes and such in J.K. Rowling's wizarding world. Still, once you think about it, you just can't stop thinking about it.