One of the special things about speculative fiction is how it can help people place themselves in situations which are entirely foreign to their experience. Sometimes this takes the form of being a space ship pilot, a member of an elite scientific team, or a wizard with arcane power and knowledge. This can serve as a form of escape, but it can also make us think about how different cultures would operate, and ourselves in them. Occasionally, we can even transfer some of those ideas to our own world. Instead of, or in addition to, being a space pilot or a wizard, sometimes speculative fiction makes us wonder about ability and disability: having extraordinary abilities or lacking ordinary ones.
Disability is present in many speculative fiction works, old and new. There are works where disability is a central element of the plot, such as Lock In, by Scalzi, and many others where it's a side element, such as Aurora, by KSR (one of the very rare books I've read with a developmentally disabled protagonist). It often feels as if disability must be justified by the plot: there aren't that many books where a character just so happens to be disabled, for no particularly plot-relevant reason. A common temptation in speculative fiction is giving disabled characters compensating superpowers. A good example of this is Robert Heinlein's Waldo, or the Sword of Truth series' treatment of Adie's bllindness. The desire for a happy ending often prompts writers to look for some form of cure or solution for their characters' disabilities, though in real life we must, most often, learn to cope with things as they are and go on.
Still, there are works that don't appear to relate to disability directly, but a small change of viewpoint shows us otherwise. When speaking about disability, it's worth considering the social model. Under the social model of disability, what makes a person disabled is not their particular body or mind, but the way society expects bodies and minds to behave. For example, people aren't disabled if they are 1.8 meters tall, because that is considered normal in society and everything is built with that in mind. Someone who is 1m tall, though, will find considerable difficulties. Likewise, humans cannot see infrared or ultraviolet, and this is not considered a disability, but someone who can't see the spectrum in between is blind, and as our society is designed around sighted people, being blind becomes an obstacle.
Under this view of disability, we can look for disabled people in works where society is organised around some capability some people lack. Let us use Harry Potter as an example.
In Magical Britain, magic is a normal ability. Like strength or visual accuity, some people have more and some less. Like a skill, some people train it further than others, and in different directions. But lacking magic completely makes one an outcast. For the most, magical society is completely separate from muggle society, and muggles are at best benignly ignored. A lot of the conflict in the books refers to the way that muggles should be treated, but this is not the only way disability presents itself.
What is a werewolf? Sure, it's a wizard who has been infected by a magical ailment and who transforms into a wolf when the moon is full. How is this different from a disability? During their period of transformation, werewolves can be dangerous to themseles and others, which leads society to shun them, although there are mechanisms to ameliorate their condition, like the potion Snape brews for Lupin. Werewolves are presented in a more ambivalent way than muggles. Many of them enjoy spreading their condition and like causing pain to others, and even characters who are considered good and kind are often sceptical about them. This resembles the way many people see mental illness. Although most forms of mental illness are not dangerous to third parties, a lot of prejudices exist about crazed killers.
Other cases are more borderline, and could be looked from a prism of racism (which is the one usually brought up when thinking about muggles) as well as disability. Beings and so-called beasts such as goblins, vampires, centaurs, giants or house elves are clearly sentient to some degree, but have a different mix of abilities than magical society is prepared to deal with. This results in treatment that is at best paternalistic (the way centaurs are given portions of wild lands by magical society), hostile (such as goblins get), or horrifyingly inhumane (the fate of house elves).
Although, for the most, Harry Potter and his friends try to treat people with dignity, an interesting case is that of Argus Filch. Argus is the Hogwarts' caretaker, and is a squib (i.e., a child of magical parents who can't do magic himself). We get to see Argus from the viewpoint of Harry Potter and his friends, and now and then other members of staff, and so we get a pretty negative opinion of him. He's unpleasant, obsessed with rule following, friendless, has only a cat for company, and takes sadistic pleasure on punishing misbehaving children. Yet we could try to look at Argus' life from a different angle.
Argus is a squib in magical society. In effect, he is a muggle condemned to live surrounded by those who despise him or think nothing of him. He works at a school where he must see magical children improve their skills every day, on their way to successful lives as magical adults, while he's stuck on a menial, dead-end job that he got from the school's headmaster as charity. It is the sort of job that's thankless and endless, and which requires a great deal of physical drudgery that could be made far easier with magic. In the Harry Potter books, we find Molly Weasley orchestrating complex cleaning and cooking tasks with the use of her wand and so-called household spells. It's clear that there are magical techniques that could make keeping Hogwarts in shape a breeze, but Argus can't use them. On top of it all, students being students, no-one cares about his work, or making things easier for him.
We know Argus doesn't get much of a reward for his devotion to his job: he doesn't get much money, as he's described as wearing moldy or moth-eaten clothes; and he doesn't get respect, as he has no friends and he goes to the ball with his cat. Everyone bosses him around, students torment him with impunity and even Peeves, a poltergeist, is allowed to spoil his work and tease him without consequences. The only person who seems to care a little bit is Dumbledore, and he doesn't care enough to make Argus' situation any less intolerable.
This treatment of Argus isn't the only case in which muggles are dealt with badly, even by good characters. Magical Britain treates the muggle parents of magical children in a way that is highly reminiscent of the way society suspects disabled parents in the real world. For instance, muggle parents have no say about sending their children to a magical school where they are subject to physical danger as well as bullying and teasing from staff and students alike for being muggleborn. The assumption that magical children must be with their own kind and muggles aren't capable and responsible enough to raise them is quite similar to the way disabled parents are often treated. Even the laws are set up to promote muggleborns to spend the summers with other magical families, since that way they can practice magic, but they are forbidden to do so even with parental permission (muggles don't count). The extreme case of this is Hermione erasing her parents' memories and sending them to live in Australia.
None of these things is presented in the book in the language of disability, but a lot of it can be looked at from the viewpoint of the social model as people being made disabled by their society. The reactions to it in the book are not too different from the reactions disabled people get in real life: paternalism, charity, patronising kindness, hostility, abuse, exploitation, and very occasionally the thoughtful, equal treatment we all wish to get from our fellow humans.
This article doesn't intend to single out the Harry Potter series for criticism. The fact that I can see all these things in it points out that it treats a lot of interesting themes. It's simply making the point that disability isn't something that we have inherently, but something society ascribes to us, and that we can see it operating in many of our favourite works of fiction, by this or by any other name.