[JackC]

> Then blacksmiths in the Middle Ages did not 'understand' the forging of swords. Only modern materials science allowed us to 'understand' why forging creates harder metal.

The interesting way to construe the article's claim is not that it's impossible to know everything, but that's impossible to know everything that people already know about the field you work in.

Were there blacksmiths who knew everything anyone knew about forging swords? Did Newton or Da Vinci know everything anyone knew about the various fields they were expert in? Are there farmers now who know everything anyone knows about how farming works? The article claims that at some point it became a certainty that programmers cannot know everything that anyone knows about how to use the tools they use and what those tools do. The stack is too complex. That's at least a sensible and interesting claim.

[Confusion]

No blacksmith, farmer or famous scientist/artist/Renaissance man in history has ever known everything there was to know (about the field they worked in). Even back then, there was already more knowledge being produced than they could possibly ever obtain. As with us, the ultimate problem is a lack of time. Whether the time required to travel to a neighbouring city to learn from their guild or the time required to read a paper on the internet, the problem is time.

All stacks have always been too complex. A farmer, to produce optimally, has to understand everything there is to know about meteorology, biology, sociology, economics and earth sciences concerning his specific area. That has never been the case.

In that sense of 'understand', nobody has ever completely understood any system they worked with/in. Given a system and a person, you can come up with a legitimate detail question about the system that you also believe the person couldn't answer.