There is a thing called functional illiteracy [1], where people can write and read but mostly only their name and some very basic things like grocery lists. They also cannot comprehend texts even if they can read most words. It's more or less equivalent to being able to add numbers, maybe multiply numbers 1-10 but very far from algebra.
No first world country can claim a 99% literacy rate unless you count in these people, which would stretch things quite a bit.
I would be surprised that a psychiatrist would find it a useful term - in the same way that any doctor would not look at the paralympics and see only one illness / disability but dozens of conditions.
I am fairly certain there are Rain Man like people who can do algebra or calculus but would for most people sit under the term "disabled".
Perhaps it might be good for you to ask, "the people I see who can do algebra also can act in certain other ways, socially and mathematically. How much am I looking for people who can do maths, people who can do maths like I do, and people like me who can do maths"
Edit: yes I suspect I sit to the left of you, but the important takeaway here is not that some people are more "intelligent" than others (I agree for whatever definition we choose) but that raising the education level of all in society massively benefits us all. Oh and ranking peoples value in society based on intelligence is not a good idea. It's only just above ranking on physical disability, or your parents aristocratic connections.
I gave no indications that people ought to be ranked in terms of value to society based on intelligence or any other criteria.
Their argument was purely an philosophical one, stating that a well informed society operates better, makes better decisions, ect. And a well educated person can make better decisions for themselves and have a higher quality of life.
The reason that universal education caught on was because large businesses realised that could have more efficient factories if they didn't have to teach everyone to read. Thus college and university because the place where the 'universal education' dream could be realised. Where every person could go and receive an education that would afford them a higher quality of life and allow them to better engage with the world.
Then, factories became more specialised and 90% of universities became slaves to some "industry"
Many universities "computer science" programs are hardly that. Rather they've turned into a coding bootcamp with slightly more math.
But there is a reason 2nd graders dont do book reviews of classic literature. Even though they can absolutely read the complex words out loud on autopilot any day of the week.
Edit: Actually, I think your premise is wrong. Children don't read words they don't understand "like muscle memory". The differences in meaning between, idk, betrothed, engaged, wedded and living in sin are superficial but they carry with them implications of social value, history and more. Children are supposed to read books and pick up context and understand meaning as they go along. We don't expect a 10 year old to grok calculus any more than we expect them to grok social/sexual arrangements. But we have different standards for 19 year olds - in the case of sexual arrangements it's obvious why. Perhaps less so for calculus.
Reading and comprehension levels are hard to guage for this reason - at a certain point the words are placeholders for political positions. And it's hard to tell if someone does not understand the word or disagrees with the politics. Please see every election for past ten years for reference
It's known that intelligence can be significantly negatively affected by environmental factors like malnutrition (both of child and mother during pregnancy), childhood disease, pollution and injury, and there is some evidence (also mentioned in the article we're discussing) that a century or two ago the average person was significantly dumber than now, presumably because of those factors - especially to the poor and women, which often experienced more severe childhood malnutrition than their male siblings.
So it would seem plausible that a hundred years ago a nontrivial percentage of people actually were too dumb to succeed in literacy and perhaps the fix for that wasn't just starting young enough and putting effort in, but rather that we started getting much fewer kids with severe environmental damage to their intelligence.
The richest kids at my highschool were also the smartest. There were one or two rich kids who didn't make honor society. There were also only a 5-6 smart kids who were middle/lower-class. Graduating class of ~500 in 1985, about 50 honor society (top 10%).
I can definitely say that there are many people for whom it is a struggle - even those on college courses.
But a hundred years ago we could easily have the same conversation about simply reading and writing - they (the poor, women, or "lower class" ) luke not be taught to read. But it turns out that if you start young enough, and put enough effort in, 99% of everyone can learn
So, perhaps society is not putting enough effort in, or asking enough effort from, our kids for them all to learn calculus.
As the Agile Manifesto says, the work delivered represents the effort input so far. If society wants all children to learn calculus, we need to pay that price.
Edit: I think that we do need a new conversation about education. We have My father left full time education at 14, at 18 most of my peers left school and only 25% of us went to college. Today it's 50% it the total spend has not gone up in line.
I honestly don't know what kind of world the "universal education" advocates of the 1870s were imagining - but I am damn sure it was not people doing college courses on their iPhones, but it is the world they ushered in.
We need to double down on what worked for the 20th Century (and avoid the, y'know wars and genocide and stuff).
Education will lay at the heart of that.