It’s a pretty interesting point.

If a large fraction of the population can’t even hold five complex ideas in their head simultaneously, without confusing them after a few seconds, are they literate in the sense of e.g. reading Plato?

I hope they're literate to understand we're only reading about that alleged exchange because Plato wrote it down.

Median literacy in the US is famously somewhere around the 6th grade level, so it's unlikely most of the population is much troubled by the thoughts of Plato.

I’d be really curious to see metrics on literacy broken down by other criteria. What’s the median literacy of people who are “like me”?

I looked up those stats. First of all, it is literacy in 'English'. A good portion of the country does not speak English at home. Second, it was assessed in 2003, and a disproportionate amount of those with 'below basic' prose literacy were over age 65 at the time. The assessment before was done in 1992 and there was an a marked increase in quantitative literacy between the two.

* https://nces.ed.gov/naal/kf_demographics.asp

What makes an "idea" atomic/discrete/cardinal? What makes an idea "complex" vs simple or merely true? Over what finite duration of time does it count as "simultaneously" being held?

Whatever you want them to be?

I don’t care about enforcing any specific interpretation on passing readers…

> can’t even hold five complex ideas in their head

As an aside, my observation of beginning programmers is that even two (independent) things happening at the same time is a serious cognitive load.

Amusingly enough, I remember having the same trouble on the data structures final in college, so “people in glass houses”.