A Predator of Information

Since I've complained about this deserving a good answer, I may as well give as good an answer as I can. This discusses surgery, eugenics, and radical changes to mind and body. If that sounds like something you wouldn't enjoy, read something else.

Bodies are Weird and Messy

Consider the eye. We can transplant in new corneas and replace clouded lenses with shiny new synthetic ones. Retinal implants aren't particularly good compared to average eyesight yet, but for some people they're life-changing^[1]. It is not unthinkable that we could treat everything from retinal detachment to cataracts by replacing the whole eyeball. So, no more blindness. Right?

Obviously not. Lesions on the visual cortex are not unknown and can impair (or destroy) visual recall and imagination as well as sight. In my own case, the optic nerve is about a third the usual cross-sectional area, with macroscopic changes propagating through the optic chiasm and into the visual cortex. Plugging an eye with 20/20 vision in to me is not going to fix this.

This is the case for most disabilities. Cochlear implants don't do anything if the issue is downstream of the cochlea. Spinal cord regeneration wouldn't help problems in the sensorimotor cortices. The proximate cause of most disabilities being relatively tractable should not be confused for all disabilities being fixable. Otherwise you set up a world where the remaining disabled people have no accommodation at all because the general perception is “There are no disabled people. Well, maybe three at most.”

I don't think central nervous system issues are fundamentally intractable nor that your brain has some magical Soul Homunculus in it and Must Never Be Touched, but doing so is much more difficult, and may (at least for a very long time) involve trade-offs like fixing your vision at the price of losing every visual memory you had from before.

An Ounce of Prevention?

You might ask why we can't just screen and genetically engineer problems away. We already do this to some degree with things like Huntington's and Tay-Sachs disease, and these are the best candidates for such a thing as they are caused by a single gene that can be tested for and cause horrifying central nervous system degeneration followed by death.

What about my visual disability? It's monogenetic. Couldn't we just screen it out? Possibly we could. I wouldn't feel particularly wronged or that I'd suffered some dignitary injury by this. If, through some change in environment or whatever, it just happened to be the case that nobody with a visual disability like mine were ever born again, I wouldn't feel wronged if people didn't intentionally engineer it into folks^[2].

The difference is that a visual impairment is a serious problem because the infrastructure of the world is built assuming a certain visual acuity. We should accommodate people with neuro-degenerative conditions as much as possible, but dementia and pain are still dementia and pain, whatever the world looks like. I don't suffer from not seeing well, I suffer from not driving in a world designed for cars and from the Vile Offspring of Steve Jobs actively removing the UI customizations that made computing so accessible in the first place. Many Deaf people say they suffer from being forced through oralist education and a lack of sign or captioning, not from deafness. Obviously there are edge cases like locked-in syndrome where some affected people have expressed a preference for nonexistence, but overall disabilities aren't torment in themselves.

This could also be called ‘Bodies are Weird and Messy, part 2’. I am also bipolar^[3], which is hereditary but not in a straightforward way. There seem to be multiple genes that can each increase the risk as well as environmental factors. A lot of things work like this, and some of the contributing genes seem at present to also contribute to generally desired traits. We don't know how to screen with any effectiveness.

Many disabilities are caused by environmental factors (toxins, injury, whatever.) People who are blind from birth generally do much better than people who have to relearn how to do everything later in life, as I've seen trying to help people who lost a lot of vision as adults but could still see better than I can. A focus on genetics over accommodation would remove the disabled people who are the best off, but do nothing for those who would have the hardest time of it.

There are also reasons to think there is value in diversity of thought and experience to society generally, and accommodated disabilities, where people experience, think about, and interact with the world in different ways while still being first-class citizens, provide a lot of that.

They May Prefer It

Let's go further into the future and ask two question: If I could take a pill that would fix my eyesight with no downsides like loss of visual memory, would I? And if I could take a pill that would make my mental/psychological configuration normal, would I?

Regarding eyesight, quite possibly! I'd want to make sure I could take a lot of time where people aren't depending on me for anything, because I'm pretty sure the world looking entirely different is something I would have to get used to. Other people may choose differently; if they are effectively first-class citizens, they might think having the faces of their loved ones look different than they remember is far too high a price to pay, or they might worry it would change their aesthetics or relation to art in a way they don't want.

Regarding bipolar, no, Absolutely not. Based on talking to other people, I know I'm in a minority. I don't think of myself as a very broken normal human, I think of myself as a pretty good something-else that could use a bit of improvement. In a world where you could fix any disability, I wouldn't want mine fixed, I'd just want to prevent the infrequent-but-terrible full mixed state, be a bit less prone to losing the ability to know when I think something is a terrible idea, and put a pretty shallow floor on the depth of depression.

One deaf student I worked with told me she would have no particular interest in gaining hearing. If she could suddenly hear the next day, she'd still have to learn to understand heard language. Being able to hear music might be nice, but she doesn't feel the lack any more than she feels deprived by not seeing flowers the way bees do. That's a perfectly reasonable answer. Me, if given the chance, I'd love to see flowers the way bees do or experience the sonar-world of a bat. Both answers are perfectly good answers.

The Red Queen's Ratchet, or Everyone's Disabled in the Future

Disability exists at the intersection of ability and the environment. In general, people with total anosmia are less disabled than people who merely have a partial impairment in sight or hearing (and some who are anosmic from birth don't realize there's a sense other people have that they don't until later in life) simply because the world isn't built on smell, except in a few specific professions. Dichromatism is a minor disability in our current world, but in a world where people shared my combination of good color perception with terrible-everything-else-visual, it would likely be a pretty severe one.

The average human's repertoire of ability was determined^[4] by the ancestral environment, but we're at the point where we've built our own rather different environments. As an example, a psychiatrist once pointed out to be that people with bipolar in the past who had unproductive periods weren't penalized for it nearly so much as now, because there wasn't the same expectation of an Unbrokenly Productive Gapless Resume, so it was easier to be much more productive than average sometimes and less at others.

If you imagine a world where we can both change ourselves relatively easily and move into or build new environments, it seems that there are only a few stable outcomes.

Consider seeing ultraviolet as its own, distinct color. You get wider, more colorful rainbows. You might even get a new line of purples between green and ultraviolet. Harmless and fun and good. But, if lots of people get the change, they're going to want to use those colors in things they make. More as it becomes more common, until mentally the assumption is that most people can see it and people start using it to communicate meaning. That pushes more people to get it, and makes things even worse for the people who don't.

Even for something innocuous, it's easy to imagine ways that it could be assumed that everyone is capable of it and build the world to match, thus there's a potential for a constant underclass of people who are the least comfortable changing themselves. This is pretty bad. Above, I gave an example of how I'd not want to change myself even though it would likely make my life easier. Pushing people to violate their notion of who they are and what matters is terrible^[5].

Consider different environments. The SF trope of space-station inhabitants with arms instead of legs, or aquatic-mammalian humans living in the ocean. Having to remake major parts of your body when traveling would cause great distress to a lot of people. This all compounds when you get to cognitive changes. An area with a high proportion of people with an expanded or reorganized working memory might start using Fith-like syntactic constructs for emotional and rhetorical effect. I suspect many people would feel wronged at being pushed to have brain surgery to understand the local language.

Thus, it seems to be that only a few possibilities exist:

Permanent Underclasses

Whoever doesn't keep running to fit the fashion gets left behind.

Bioconservatism

Everyone has to be a Normal Human. As defined by whoever's in power. This might be defined as ‘unmodified and containing no genes not passed down from unmodified parents’. It might simply be a legal code requiring all people to accept a certain set of abilities and details of configuration and forbidding others.

Segregation

Everyone lives and communicates with ‘their own kind’, throwing out all the advantages of a lively society where wildly different people share and influence each other. Also, it really sucks if there aren't many of ‘your own kind’.

Universal Access

Embrace the idea that some 'set of abilities' is not universal either locally or globally, and that this will likely become more the case with time. Build a world for everyone with that assumption.

How?

Asking how to enact universal access is a bit like asking for a blueprint for a complete socialist society. It's a good question, but we don't yet have a complete answer, because the territory has yet to be thoroughly explored. You start where you are and make suggestions that would make the world a bit more like your ideal, and as you explore you get more ideas where to go^[6].

The basics are kind of obvious. Think of universal access from the ground up. Don't say “We have data saying this is easiest for people to read^[7], so that's what you get.”

Remember that, in the present, it's very likely you'll end up disabled in some way if you don't die young. I know at least two older couples who had to move simply because the places they lived had no bathrooms on the ground floor and as they aged they couldn't handle stairs well. The idea that disability is something that happens to other people is not a safe one to hold.

Don't expect people to be able to easily provide a convenient name for their circumstances that you know about, nor should you demand they conform to your idea of what their needs are. Your expectations may be wrong. You may not have heard of their condition. They might not know the name, or they might know it but think it doesn't apply to them, because hermeneutical injustice is actually a serious problem.

Beyond conscientiousness and building accessibility in from the beginning, assuming you'll not think of every accommodation someone might need and adding enough slack, space, and flexibility that they or someone else can add it later seems the best I have for now.

Footnotes

[1] And sadly life-changing again when the corporations behind them suddenly abandon a line but won't release any of the information about how to repair, upgrade, replace, or maintain it. Cybernetics under capitalism is simply a nightmare, under IP-cartel capitalism, doubly so.

[2] I do not privilege nature, nor do I have much patience for people who do.

[3] Lived experience is not analysis, but it is a useful input. I'm leading with my own circumstances because I can say why a specific disabled person (me) might prefer one thing over another. Other disabled people may choose differently.

[4] Imperfectly, approximately. Never forget, evolution is a very slow hill-climber and local maxima are a thing.

[5] One reason I've always hated the 'immutable characteristic' test. So we invent a way to turn gay people straight. So what? Does that suddenly make it okay to bully people until they let you jab them with something that changes how they feel about their romantic partners? Their dating life? People who are into sex often feel it's one of the most personal and emotionally potent things about them.

[6] One of the reasons I have no patience for Marxism-Leninism or other revolutionary, vanguard party approaches. To me, it seems the exact opposite of how you explore, adapt, and learn from people's experiences.

[7] The same data show, much to the surprise of many left-handed folk, that humans are universally right-handed.