I think this idea is basically nonsense. Some things are complicated. To "explain" them in simple terms you necessarily leave out a lot of information. If all that information isn't crucial to the core idea, maybe that's worthwhile. But sometimes that information is crucial.
Some people look at advanced mathematics or physics and wonder why it has to be so complicated and so full of jargon. It's complicated because it is. The jargon, believe it or not, is mostly an attempt to make it easier to communicate. It would be very, very difficult to wade through these ideas without introducing new words with precise definitions.
Then again, John von Neumann said, "In mathematics you don't understand things. You just get used to them." So maybe the title is true for trivial reasons after all.
It's not nonsense. You are forgetting a very important detail: "explaining".
He was not talking about writing a research paper on the simplest possible terms. Rather, about "explaining" a subject. When we are explaining, we always have to deliberately omit details to get the basic idea across, so that the other person can form the initial mental image. Sometimes we also have to resort to metaphors and comparisons from entirely different fields, or relate them to real world concepts.
Once that is done, then the lengthily process can begin on improving the fit of that mental image to the subject. This will require more explanations, more focused, in a different level of detail.
Case in point: dimensions higher than three. Most people cannot conceive what the heck a tesseract is, or why it is usually drawn the way it is. But then you can tell them to watch Feymann's Flatland scenario, and they will be able to understand the basic concept.
Are they mathematicians now? Hardly. But now they have some understanding on the subject which they did not have before, even if it is on a very high level. And can try to absorb more details, if so inclined.
Er, they may be left with a warm and fuzzy feeling that they have some "understanding", but let get them to do some multidimensional analysis and see how they do. The meaning of "explaining" seems just as elusive as the "simple explanations" themselves - once you've heard such a "simple explanation" and have a feeling that you now understand more than you do, what is the objective difference between you-before and you-now? It's my experience, and several professors have confided the same, that the "simple explanations" give students a nice feeling that they "get it", up to the point where they actually try to apply the knowledge and fail miserably. Maybe the explanation then wasn't really "simple", but now we're just shifting the goalposts further into epistemology.
I would tentatively agree that there is a skill which allows you to break down complex subjects into digestible chunks, but that usually depends a lot on the student as well as the teacher(e.g. some people are good at following metaphors, others learn very well from repeated examples, etc), but the outright statement in the topic suggests that there is no such thing as irreducible complexity, which seems ludicrous.
> "Er, they may be left with a warm and fuzzy feeling that they have some "understanding", but let get them to do some multidimensional analysis and see how they do."
Nobody's having any delusions that explaining is the same as teaching. You can explain multidimensional analysis simply if you understand the subject fully, however you can't teach something to someone else unless they work with you and try it out themselves.
But if you want to explain to your politicians that hospitals need special machines to do radiation therapy you don't enroll them into nuclear physics 101, they can probably do with a very broad explanation of how radiation works.
Remember that repetition is the heart of learning. If you want someone to understand Relativity to the same degree Einstein understood it, you don't start with the math. You start with an analogy (which obviously doesn't match reality). Once they understand that you can add more analogies (maybe about just parts of Relativity). Eventually you build up from parts to the whole and from broad analogies to specific details. Over the years this is happening you will be gradually introducing shortcuts and jargon. But, only a master of the subject can explain a complex topic in simple terms. I can't tell you how many times my children have asked me a question about something I thought I knew, but once I started trying to explain it in terms they would understand I realized that I really didn't understand what I thought I understood. But if I spent a little bit of time reading up on the subject again then I found that I could explain it to them in such a way that they could correctly explain it back to me.
I see it as an analogy with how, in maths, to fully understand a complicated concept you must be able to explain it using more and more basic definitions, but that does not mean you have to express everything in basis to fundamental axioms, just that you could.
Maybe explaining a complex concept in simple terms would take you 2 hours, 12 hours or 3 days, but you can do it if you really understand it.
Some people look at advanced mathematics or physics and wonder why it has to be so complicated and so full of jargon. It's complicated because it is. The jargon, believe it or not, is mostly an attempt to make it easier to communicate. It would be very, very difficult to wade through these ideas without introducing new words with precise definitions.
Then again, John von Neumann said, "In mathematics you don't understand things. You just get used to them." So maybe the title is true for trivial reasons after all.