
If you can’t explain something in simple terms, you don’t understand it - daschaefer
http://kottke.org/17/06/if-you-cant-explain-something-in-simple-terms-you-dont-understand-it
======
freddref
Feynman also said:

"Hell, if I could explain it to the average person, it wouldn't have been
worth the Nobel prize." [1]

Showing a limitation of the maxim or Feynman's hubris?

[1]
[https://en.wikiquote.org/wiki/Richard_Feynman](https://en.wikiquote.org/wiki/Richard_Feynman)

~~~
squeaky-clean
A lot of people seem to be conflating the idea of explaining something to a
layman, and explaining something using simple terms.

~~~
Jach
A math formula is one of the objectively simplest ways of expressing
something. But it's not easily understood unless you know the math well, thus
violating Gruber's rule. Feynman was honest about this, because magnetism can
be explained very simply, but not in any familiar way to things most people
already know about.

At least as good as math (and capturing the objective complexity better I
think) is a working program. "What I can't program, I don't understand."

When people ask for a simple explanation, they usually expect it to be easy
for them too, because we all want simple and easy at the same time, even
though only one of those is objective. If your reply to "how do magnets work?"
is to start by writing down Maxwell's equations, you're gonna get crap for it,
but someone who uses the fake rubber band analogy will be well received. But
who really understands magnetism better?

~~~
xg15
But I think that's the deeper point of the "if you can't explain it, you don't
understand it": Sure, you can write down the equations, but then what exactly
have you done? You wrote down some string of characters and showed that it can
be derived from some other strings of characters by applying a series of
arbitrary-looking rules. By itself, that doesn't tell anything. It's only when
you manage the connect formula to the part of reality that it tries to
describe - and connect that part to the rest of reality - that it gains any
sense.

Trying to explain a concept in "simple terms" forces you to view it in terms
of its connection to other, well-known phenomena.

~~~
throwaway3535
> You wrote down some string of characters and showed that it can be derived
> from some other strings of characters by applying a series of arbitrary-
> looking rules.

At this point it's turtles all the way down.

~~~
xg15
No.

That's what it looks like if you _only_ look at the formula. (And why I'd say
that formulas are not an "objectively simple way of expressing something*)

If you can somehow keep in mind what the formula is supposed to represent, the
operations on characters will let you find some insight about that thing and
will stop standing only for itself.

~~~
Qwertious
The point is that the term "simple" is _inherently subjective_ \- there are
plenty of concepts that are simple and intuitive once learned, but are hard to
learn.

Also, mathematical formulas are essentially a different language. If people
don't speak it, then it's a moot point.

------
ivanbakel
The problem I find with this outlook is that it takes technical terms being
jargon at face value. If you can't fall back on progress in language which
allows you to express more complex ideas, you're not going to reach the same
depth of understanding in simpler words without it taking a lot longer anyways
- with most of your time spent reestablishing what you just threw out the
window.

If you rehash it in smaller words, just by information density alone, aren't
you guaranteed to be losing some detail?

~~~
scott_s
"Education is a series of small lies." Spoken by my intro to computer
engineering professor, upon telling us that most real processors actually have
some _ternary_ logic.

The notion here is that educating beginners about a subject is different from
communication between experts. Yes, experts use jargon because it is more
efficient. But, the notion here is that if you truly understand something, you
should be able to find a way to explain it to a non-expert, building up from
words and concepts they already understand. And, further, if you _can 't_ do
that, then perhaps your understanding is not as deep as you thought it was.

~~~
Cyph0n
> most real processors actually have some ternary logic

Was he referring to the Z state? If so, it's not _really_ ternary logic but
rather a "no result" state for cases where there is a control signal involved
(e.g., in a tri-state buffer).

~~~
tlb
Modern CPUs have phase-locked loops generating clocks for each region of the
chip. These use separate pull-up and pull-down mosfets to control the
frequency, so arguably ternary.

Even more non-binary things happen inside DRAM and flash memory.

~~~
Cyph0n
Ehh I don't believe PLLs have a ternary component at all. I'm not an expert
though.

DRAM is analog-based due to the fact that the core memory unit is a capacitor,
so it can't be ternary (not digital). I might agree with flash though.

------
jknoepfler
This strikes me as raw arrogance. Complexity is intrinsic to many systems that
are subject of expert study. To tell someone who has devoted their career to
understanding a complex topic that they don't understand their subject because
they can't express it in layman's terms without doing terrible violence to the
underlying phenomenon is ludicrous.

This is the sort of thing you'd believe if you were an arrogant 20-something
who thought they could learn any subject in a few hours, cushioned thoroughly
by the illusion of understanding.

"Oh yeah, I understand the mechanisms of human vision. It's just rods and
cones."

"I understand the causes of the American revolution. It was just people
protecting their property."

"I understand Joyce's Ulysses. It's just follows three people from Dublin over
a single day. I read the Cliffs notes."

"I understand why coffee makes me alert. It's just blocking some brain things
that make you sleepy."

Now, I will agree that if you don't know how to break interactions down into
teachable parts, you will probably have trouble as an engineer or scientist
both advancing your own knowledge and introducing people to the field. But to
suggest that your understanding of a subject hinges on being able to deliver
an explanation in simple terms is just silly.

~~~
api
I strongly disagree.

Complexity is real, but understanding means being able to conceptualize a
system at such a high level that it becomes possible to convey the most
important key ideas simply. This may involve some amount of over-
simplification (which should be indicated if present) and will undoubtedly
leave out a tremendous amount of detail, but the conceptual essence should be
there.

The inability to do this is IMHO a sign of either lack of true and deep
understanding or communication ability.

There are fields where nobody can really do this. These are fields that nobody
truly understands yet.

Edit:

Let me give you an example. I had a bad (but typical) math prof in my very
first calculus class who covered the board with examples and took us through
how to differentiate a function. I was completely confused and stuck. Then I
called my father on the phone and asked him and he told me "a derivative is a
rate of change." Then I got the rest of calculus.

The prof had talked about _slope_ but that wasn't conceptual enough. I needed
"rate of change." That is the essence of calculus. It's the most important
concept. Calculus deals with rates of change and the inverse (integrals). Once
this concept was communicated the rest of calculus became possible to
understand.

If you can't do that for a given area, you don't understand it or (as was the
case with this math prof) are a poor communicator.

~~~
rrdharan
> This may involve some amount of over-simplification (which should be
> indicated if present) and will undoubtedly leave out a tremendous amount of
> detail, but the conceptual essence should be there.

I think the disagreement hinges on whether you believe the snippets from the
GP post e.g. the "rods and cones" or caffeine examples are fundamentally
valuable or not.

> There are fields where nobody can really do this. These are fields that
> nobody truly understands yet.

Curious what you would consider an example of such a field?

FWIW my anecdotal example of what I think the GP is complaining about... I
read "The Elegant Universe":
[https://en.wikipedia.org/wiki/The_Elegant_Universe](https://en.wikipedia.org/wiki/The_Elegant_Universe)

It's a good book, and I enjoyed reading it. But over subsequent years I've had
growing doubts over the true value of the "understanding" that it provided.

~~~
api
> Curious what you would consider an example of such a field?

The frontiers of physics always strike me this way. The names and explanations
are incredibly strained and bizarre. This is probably the canonical example
and is perhaps why The Elegant Universe doesn't quite achieve what it sets out
to achieve.

Another one from my own academic past is "complexity theory" where hand-wavey
concepts like "emergency" or "higher order causation" get thrown around with a
lot of confusion. We can clearly see there's some "there" here, but I don't
think we really understand what it all means yet. Put stuff together,
interesting higher-order stuff happens, and so now let's create a
combinatorial explosion of jargon around it. Publish or perish.

Finally "consciousness studies" or anything else semi-fringe probably counts.
Again there's certainly some "there" there, but we don't even know the right
questions to ask. Something is happening to matter that makes it wonder what's
happening to it.

------
jancsika
This Feynman quote from the article is put in the wrong context:

> I really can’t do a good job, any job, of explaining magnetic force in terms
> of something else you’re more familiar with, because I don’t understand it
> in terms of anything else you’re more familiar with.

The article implies this is a case of the scientist expressing that he didn't
understand a thing. But watching the video in full[1], one realizes he is
saying something different:

"It's a force which is present all the time and very common and is a basic
force.

[...]

I can't explain that attraction in terms of anything else that's familiar to
you. For example if we say that magnets attract like as if they are connected
by rubber bands I would be cheating you because they're not connected by
rubber bands-- I should be in trouble if you soon ask me about the nature of
the band. And secondly, if you were curious enough you would ask me why rubber
bands tend to pull back together again, and I would end up explaining that in
terms of electrical forces which are the very things that I'm trying to use
the rubber bands to explain. So I have cheated very badly, you see."

In other words, for some phenomena the only simple examples are themselves
instances of that same phenomena. So the only possible analogies are
themselves merely tautologies.

I've noticed something less sweeping though similarly absurd with the
internet. As more and more of people's daily lives depend on internet
technologies, it becomes more difficult to find modern, simple examples for
analogies that don't rely on similar internet technologies. So someone who
wants to explain the wonders of packet switching compares it to long-distance
telephone calls, but they then spend the bulk of that time explaining long-
distance phone calls to people who have never used a wired phone.

1: [https://www.youtube.com/watch?v=wMFPe-
DwULM](https://www.youtube.com/watch?v=wMFPe-DwULM)

------
ChuckMcM
_" What I cannot create, I do not understand."_

This actually came up for me at the office. I was asking a bunch of questions
about the Z transform and the Fast Fourier Transform. The person I was talking
to said, "Hey, just call the function in MATLAB, it doesn't matter _how_ it
works, just that you understand what it is saying."

All of my life I have rebelled at this notion. My earliest recollection of
running into it was when I was in grade school and took apart three wind up
alarm clocks, each more carefully than the one previously. My Mom was curious
what I was looking for and I told her, "How does a clock know how long one
second is?" She didn't know, and I didn't know, and while I had mastered using
a clock and accepting that it would go off when I set it to go off, I didn't
really "know" how a clock worked until I had taken apart and identified, (and
modified to validate the identification :), the escapement.

~~~
jgamman
surely there's some tension between these two extremes. for someone learning
how to _use_ FFT's, treating them as a black box for a while is useful so they
can build some intuition etc and then, if it floats their boat, go back and
dive deeper. as a chemist, I didn't give a rat's how the thing worked, I had
spectra to analyse...

Conversely, if you had to deep dive everything, you would not get _anything_
done since there's always a deeper level.

Maybe it's just an experience thing where you start to appreciate that for
most things (probably all bar one or two) you are just the privileged user of
other people's expertise.

~~~
ChuckMcM
I don't think I was clear in my comment, I personally find great joy in
learning things (which makes me something of an autodidact) its just one of
those things.

My desire to understand things though has never been a hindrance to using
them. Long before I understood how compilers worked I was using them daily,
long before I understood how PN junctions did what they did I was soldering
diodes into boards.

It only generates tension when I want some tool to do something that it cannot
do, and reasoning about whether the constraint is due to the tool or the
implementation of the tool can only happen if I really understand what the
tool is _actually_ doing.

~~~
jgamman
agree. it's when something doesn't work at the edges and you desperately need
it to is when you're often ready to learn. motivation (desperation ;-) is a
marvelous incentive.

------
NumberSix
This is Feynman from the introduction to his Feynman Lectures on Physics:

The question, of course, is how well this experiment has succeeded. My own
point of view — which, however, does not seem to be shared by most of the
people who worked with the students — is pessimistic. I don’t think I did very
well by the students. When I look at the way the majority of the students
handled the problems on the examinations, I think the system is a failure. Of
course, my friends point out to me that there were one or two dozen students
who — very surprisingly — understood almost everything in all of the lectures,
and who were quite active in working with the material and worrying about the
many points in an excited and interested way. These people have now, I
believe, a first rate background in physics — and they are, after all, the
ones I was trying to get at. But then, “The power of instruction is seldom of
much efficacy except in those happy dispositions where it is almost
superfluous. ” (Gibbon)

Richard P. Feynman, 1963

[http://feynmanlectures.caltech.edu/I_91.html](http://feynmanlectures.caltech.edu/I_91.html)

Note that by his own account, most of his students did not do well. James
Gleick's biography of Feynman, Genius, has a longer discussion of the
disappointing results of his lectures to undergraduates at Caltech, many of
whom reportedly stopped attending the lectures as they were not getting
anything useful out of them.

That Feynman in fact had difficulty explaining freshman physics to the highly
qualified students at Caltech surely does not indicate he did not understand
freshman physics.

Some topics are simply very complex. It is not clear that they can always be
conveyed in simple terms. In some cases, a "big picture" explanation may be
possible but the details remain complicated. In some cases, a hand-waving
analogy to some everyday phenomenon may create the illusion of understanding
but be misleading or wrong.

To give a specific modern example, a state of the art video codec such as
H.264 is extremely complex, built of many complicated components and sub-
algorithms. While it may be possible to explain the big picture in relatively
simple terms, the detailed implementation and operation is not simple. The
inability of someone who creates or implements a video codec to explain it in
simple terms to a layman is not an indication that they do not understand it.

~~~
JackFr
The best math professor I ever had, was in a 400-level Real Analysis class.
His particular skill was that he basically had mastered the catalog of
incorrect mental models students developed.

He would be proving something in class, someone would stop to ask a question,
and from their question he would know not to try to answer it as asked, but
rather he knew they were asking the wrong question, because the question was
predicated on a misunderstanding of something three or four steps back.

Now these were proofs that a working mathematician could probably do in their
sleep, but they were a level up in terms of abstraction for most of the
students and to be able to drag us along with him was a rare talent.

------
mikebenfield
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.

~~~
outworlder
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.

~~~
Sacho
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.

~~~
pimmen
> "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.

------
makecheck
It's not realistic to expect this. If everything could be simplified to this
degree, you would never need experts.

It is also dangerous to assume this, because that is exactly how we reached
the "my uninformed opinion is as valid as your years of experience" aspect of
the current political climate. NO, things are NOT as simple as you _think_
they are just because you saw it in the space of a tweet!

On the other hand, it is important to recognize expertise over bullshit. The
easiest defense is having several experts, since at a certain point they would
need to do an awful lot of collusion to just make things up between them (i.e.
if enough of them agree then what they say is apparently correct).

~~~
pimmen
Nobody's saying that "explaining" is the same as "teaching". Nobody's saying
that "basic understanding" is the same as "mastery".

This is just to get people started, it's not a substitute for years of hard
work and study. Feynman never claimed this and I think this is missing the
point entirely. Unless you have a complete model of how the system works you
can't come up with suitable analogies to gently ease in new people to get
started.

------
startupdiscuss
This is generally true but I will add one wrinkle.

And there are three kinds of explanation:

1\. visual

2\. mathematical

3\. linguistic

So sometimes, you understand something visually, or mathematically, but you
are forced to put it into verbal terms (say, over a text only channel, or
voice), and then you may seem not to be able to explain it even though you
understand it.

~~~
specialist
I first learned about The Big Triangle from Scott McCloud's "Understanding
Comics".

[http://scottmccloud.com/4-inventions/triangle/index.html](http://scottmccloud.com/4-inventions/triangle/index.html)

[http://homes.chass.utoronto.ca/~mfram/Media/0505-UC-
triangle...](http://homes.chass.utoronto.ca/~mfram/Media/0505-UC-triangle-
all.jpg)

Filed under "I believe, but cannot prove": The three-way tension is a
recurring pattern.

When trying to understand new things, I often try to reframe things as a
triangle. When pondering intractable problems, I favor three-way solutions.
Some quick examples from memory...

Project management: time, money, scope.

aka Quality: Fast, good, cheap.

US Govt balance of power: Executive, Congress, Judiciary

Language design: imparative, declarative, functional

Pop music: harmony, melody, lyrics

~~~
thanatropism
(A name for the three-way tension you will find a lot: trilemma.)

If you have to budget something, it becomes a soft trilemma: I have 24 hours
for work + leisure + sleep, so any given combination will be a point inside a
triangle whose vertices are (0, work), (0,leisure), (0, sleep). This structure
is called a (2-)simplex.

BTW: a regular dilemma (should I spend or save) is a 1-simplex, and is a
simple linear combination a _save + (1-a)_ spend.

Now, this is fun for two reasons:

\- You can have (n)-lemmas (i.e. n-fold tradeoff structures) that are modeled
as (n-1)-simplices. Actually useful: you can do statistical inference on
simplices using the Dirichlet distribution.

\- A simplicial complex (basically, a set of simplices) can be used to build
topological spaces part by part. This kind of maths (algebraic topology) is a
whole "south part of the mountain" climb towards abstract mathematics that
bypasses a lot of Cantorian handwringing on the ultra-local structure of
topology. Instead, you're computing stuff from the get go -- and indeed one of
the emerging machine learning techniques goes precisely from building a
simplicial-like complex from data and computing characteristics of its
topology.

------
bo1024
I'm in academia and get to listen to and interact with extremely smart people
who are experts in their subject. This quote really hits home for me.

I'm not saying I'll take it as literally true in every situation. But what I
love about the quote is that _it sets the bar for "understanding" very high_.

People sell themselves short on understanding - they reach a certain level and
are satisfied that they understand something, when there is actually much
deeper understanding to be had. For example, being able to write a proof of a
theorem can be very far from understanding why it's true, but even
mathematicians sometimes pretend it's the same.

So I like that this quote challenges us to understand things more deeply. And
more often than not, I find it rings true.

(A basic example coming to mind is the determinant of a matrix. Can be
explained in simple terms to children (at least the key idea), or in confusing
terms to freshman linear algebra students....)

------
marknadal
Ah, I love Feynman. I see some other people in this thread arguing against
even bothering to do this, which is sad.

We've started doing Explorable Explanations / Animated Explainers, here are
some we've done and some that others have done:

\- Explaining how GIT works:
[http://gun.js.org/explainers/school/class.html](http://gun.js.org/explainers/school/class.html)

\- How neurons work: [http://ncase.me/neurons/](http://ncase.me/neurons/)

\- How end-to-end cryptography works:
[http://gun.js.org/explainers/data/security.html](http://gun.js.org/explainers/data/security.html)

\- How gerrymandering works:
[http://polytrope.com/district/](http://polytrope.com/district/) (by a friend
of mine!)

\- How sorting on partial data / data streams works:
[http://gun.js.org/explainers/basketball/basketball.html](http://gun.js.org/explainers/basketball/basketball.html)

And more! It is possible, it can be done. But it is hard. That is no excuse
for not trying though. Big shout out to Bret Victor's work for starting a lot
of this, and thanks to Feynman for encouraging and practicing what he teaches.

------
SiVal
Understanding something is having a good working model stored the way brains
store models, which is quite a complex network. Explaining it requires finding
a way to serialize it that makes it as easy as possible for a listener to
reconstruct the model in his own mind.

I think the effort involved in trying to come up with a serialization causes
us to more carefully examine our models, which usually improves them.

But I don't think the lack of a good serialization implies the lack of a good
model.

~~~
tshadley
You serialized that very well.

------
aeturnum
I think this is broadly true, but not in the way a lot of other commentators
mean.

Explaining something in simple terms does not mean you _fully_ explain it. You
explain the essence (or what you see as the essence) of the thing. Google
search is: you type a question into a box and Google shows you the best
answer. Google search is a lot more than that, of course, but if you can't
"boil it down" you don't understand it.

This is the top line of a git commit v.s. the comments you leave in the source
code. You can spend months working on thousands of lines of code, bur if you
can't describe it in a single sentence (while leaving a lot out!) it's a bad
sign.

------
scandox
In job interviews I always zone in on the most complicated thing someone has
worked on and then ask them to explain it to me. Often a thesis or a project
or a large system or something low level to do with OS features etc...

It is amazing how rarely people can get it across to me in basic terms. In
fact even the idea of breaking it down into non technical concepts seems to be
surprising and alien to many people.

I really admire those who can.

~~~
lcnmrn
I fail all interviews when I explain complex things in simple terms. Must be
some correlation here.

~~~
scandox
It's only one way to approach things. Many good people are not great
explainers. However, I do find a willingness to try and get down to first
principles a good sign. I only take it badly when people seem unable to think
outside their expertise, or seem unaware of the layers above and beneath the
particular strata they work within.

------
mabbo
Edit: apparently, I have been misinformed for a very long time. These are
still excellent lectures to watch though!

The Feynman Lectures are now on Youtube[0], and I like to watch them (all of
them) every few years. I highly recommend that if you've never seen them, you
take some time and watch them- _really_ watch them. Close the other windows,
turn your phone to do not disturb, and really watch these masterpieces of
education.

[0]
[https://www.youtube.com/watch?v=j3mhkYbznBk](https://www.youtube.com/watch?v=j3mhkYbznBk)

~~~
shas3
These lectures are different from his famous Lectures on Physics. The lectures
you linked to were compiled in "Character of Physical Law" and are not related
to his Caltech undergraduate courses where he presented his "Lectures on
Physics" content.

You link to:
[https://en.wikipedia.org/wiki/The_Character_of_Physical_Law](https://en.wikipedia.org/wiki/The_Character_of_Physical_Law)

"Feynman Lectures on Physics" are:
[https://en.wikipedia.org/wiki/The_Feynman_Lectures_on_Physic...](https://en.wikipedia.org/wiki/The_Feynman_Lectures_on_Physics)

~~~
mabbo
....

Are you serious?!?!

Oh shit, that's... I've been grossly misformed for a very long time.

------
octref
Or to quote PG's _Write Like You Talk_ [0]:

 _And in my experience, the harder the subject, the more informally experts
speak. Partly, I think, because they have less to prove, and partly because
the harder the ideas you 're talking about, the less you can afford to let
language get in the way._

 _Informal language is the athletic clothing of ideas._

[0]:
[http://www.paulgraham.com/talk.html](http://www.paulgraham.com/talk.html)

~~~
simplicio
Eh, I suspect part of the reason is that once a topic crosses a certain level
of difficulty, trying to convey an exact explanation for it in a reasonable
amount of time becomes impossible and experts just fall back on analogies and
hand-waving.

I'm a physicist, and if you asked me to explain Newton's laws or classical
thermodynamics to someone, I could probably give them a reasonably complete
overview in a few hours. And in doing so I'd probably introduce and explain
some jargon (entropy, derivatives, etc) along the way to make it easier.

On the otherhand, if you asked me to explain Quantum Field Theory or General
Relativity in the same time, I'd basically just give up and throw out some
friendly but inexact analogies about stretched rubber sheets and the like, and
hope the walked away with some vague sense of the outlines of the subject.

------
rdlecler1
Nassim Taleb makes a convincing argument that you first understand something
implicitly and then later it becomes formalized. I'm not sure I buy into the
idea that people with great communication skills have privileged
understanding. The underlying assumption here is that understanding is verbal.
I reject that hypothesis.

------
Animats
That works for physics, which seems to be parsimonious with its base concepts.
The equations which define most of physics fit on one sheet of paper.

It doesn't work for biology, which is complicated at the bottom. Evolution
doesn't have the parsimony of physics. Nor does it have to be understandable
by humans.

Whether it works for software is a design issue. It's certainly possible to
create software which cannot be explained simply.

~~~
dredmorbius
The essence of biology:
[https://www.reddit.com/r/dredmorbius/comments/6fupwz/the_ess...](https://www.reddit.com/r/dredmorbius/comments/6fupwz/the_essence_of_biology/)

(I'm actually really hoping for someone to show up and say, "Um, gosh, I don't
know how to say this, but that's just so wrong..." And then how.)

------
arto
Counterpoint from Feynman himself:

[https://www.youtube.com/watch?v=MO0r930Sn_8](https://www.youtube.com/watch?v=MO0r930Sn_8)

------
pwaivers
Being able to explain something in simple terms is actually REALLY difficult
to do. It is a skill in itself. Someone can intuitively understand math very
well, but lack the skill to explain it to someone else at all.

~~~
specialist
I love organizing, simplifying things. Geeks are addicted to complexity. I
think it's some kinda machismo thing.

This incompatability has caused me problems my entire career. I've more or
less stopped trying. I just do what I'm told and save my creative energy for
my personal projects.

------
mncharity
> If you can’t explain something in simple terms, you don’t understand it

And an underappreciated corollary is...

If you want something explained well in simple terms, you have to find someone
who understands it deeply.

In the sciences, that means someone who has it as their research focus.
Because as you move away from that focus, understanding rapidly becomes
ramshackle. Leave someone's subfield, and you might as well be talking with a
random graduate student (in that field). And that's hopeless.

Thus many research talks have videos and stories which would nice to have in a
K-12 classroom. And most all K-12 education content is incoherent
wretchedness.

An old essay of mine: "Scientific expertise is not broadly distributed - an
underappreciated obstacle to creating better content"
[http://www.clarifyscience.info/part/MHjx6](http://www.clarifyscience.info/part/MHjx6)
In which a 5-year old with finger paints wants to paint the Sun, but
encounters astronomy graduate students.

 _" I am sorry for the length of my letter, but I had not the time to write a
short one."_ \- Blaise Pascal 1657

There's a sad little genre of low-quality science education research that
goes: "I tried to teach topic T to students of age A. I taught it <really
really badly>. Surprisingly, that didn't work! I've reach the obvious
conclusion: students of age A are developmentally unready to learn topic T."

But understanding, while necessary, is not sufficient. At PhD poster session
practice, it's often remarkably hard to help candidates develop an "elevator
pitch". To clearly understand the core of what they've spent the last n years
working on. I'm still amazed by how often one gets something like "wow, now I
can explain it to my parents".

------
zerr
No. The teaching ability is a completely different dimension, orthogonal to
other skills/knowledge you have.

------
taurath
My favorite corollary (attribution unknown) -

"But if you can ONLY explain something in simple terms, you still don't
understand it"

------
CatMtKing
I practice taijiquan, a martial art. My teacher often describes concepts that
I can relate to basic mechanics. When I do, it feels like I understand, but as
my teacher says -- until you can actually express it with your body, you don't
really understand.

For example, a lever seems conceptually simple, but to create a lever in the
body is extraordinarily hard. The joints have to be solidly connected and free
to open or close. The direction must be precise and rotation must not wobble.
There are so many things that can err and lots of places for force to leak
out.

------
throw2016
This is eternal. The expert paves the way to understanding. Its only because
of their expertise that they can simplify and explain it in a way that others
can understand. They have a firm grasp of the concept. Understanding is not
equal to expertise, just the first step.

I think there are too many times when people affect a tone of authority and
expertise and hide their lack of understanding in verbiage and complexity
while making excuses for their inability to explain it to the layman.

------
combatentropy
I think this statement is a tautology. To understand something is to know it
in simple terms. To understand something is to have mentally broken down a
complex subject into its simpler pieces. For example, to understand a car
engine is to take it apart in your head and know each part, how it moves, and
what it does.

Many think they understand something, when really they only know how to use
it. For example, I understand how to use a computer, but that doesn't mean I
understand how a processor works at the level of registers and assembly
language. So if I were to try to teach someone a computer, then I could say
things like "Click that, and this will happen," or "Type such and such, and
then this other thing you want will happen." But if anyone asked me about how
that actually works, to follow all the way how a physical mouse-click gets
transformed into a change in the window on the screen, then I couldn't. Or,
even if I could, it might take me half an hour to explain it, depending on how
much they want to know.

So maybe it's that we undestand things, but at different levels. Few people
understand something at its deepest level. In fact, physicists would say no
one does.

------
sh87
This is an interesting logic fallacy here. Consider this example.

Monkey eat => Monkey live.

Monkey live => Monkey eat.

Monkey not eat => Monkey not live.

Monkey not live => Monkey not eat.

Here "=>" is used as in "implies"/"because". The last statement is weird.
There are more ways for monkey to "not live" than to "not eat".

Not being able to explain does not imply not being able to understand. Not
understanding surely implies not being able to explain.

Correlation, Causation, get it ?

~~~
tgb
"implies" and "because" are not equivalent. For example, "x is positive
implies x^2 is positive" is true but "x is positive because x^2 is positive"
is false.

~~~
sh87
exactly what I was trying to point out. It came out wrong I guess.

A statement like "if not a, then not b" is not applicable unless a "implies" b
and a "is because of" b.

Correct me if I got it all wrong somehow.

~~~
tgb
"if not a, then not b" is equivalent to "if b then a" and is neither
equivalent to nor the opposite of "a implies b". I'm having trouble
understanding your point under these confusions. Is it that being able to
explain is a sufficient but not a necessary condition for understanding?

~~~
sh87
Point taken. My point is just because I can simply explain it does not imply
clear understanding. And not being able to explain isn't a reliable indicator
of lack of understanding

------
moarrgan
I feel like a lot of the commenters here are making a false assumption,
arguing "just because you can explain something in simple terms doesn't mean
you understand it - look how much nuance and complexity gets lost!" That
statement makes the assumption that you must explain the subject to another
individual to the point where they understand that subject as well as you do.
Well, obviously you are going to lose complexity, just on the basis of
explaining something in _simple_ terms. The point is that if you cannot
distill something to its core ideas to the point where someone else will gain
a _basic_ understanding of that concept, then you do not understand what its
core ideas are, and therefore do not understand the concept itself. No one is
arguing that what took you 10 years and a PhD to understand is something you
can explain "simply" to someone and they will emerge with the same level of
understanding as you have. No, they will emerge with a _basic_ understanding
of that concept if you have explained it well.

------
killjoywashere
The author is not a student of physics and didn't go through Feynman's
lectures. Some of the stuff Feynman said may sound like the droll wisdom of an
ancient wizard to laymen, but if you've studied physics, it sounds more like a
fun introductory confection. The layman hears genius, a journeyman hears the
chef's description of this evening's specials.

------
olegkikin
That's just not true, it's confusing explanation and oversimplification. Many
complex things require years of study just to understand that thing even in
the most simple terms. Try and explain string theory to someone who has no
idea of particle physics, colliders, quantum theory. At best you can make up
some abstraction which doesn't explain anything.

------
lngnmn
This is how to distinguish a cosplay of intelligence from true intelligence,
among other things.

The Buddha and the Upanishadic seers were exceptionally good with explaining
complex phenomena in simple terms.

Apparent sophistication is a sign of a confusion. Clarity is an evidence [of
deep understanding].

Nature is vastly complex but not complicated (a few fundamental laws at work).
Only simple things work.

------
simlevesque
In french we have a saying which translates to: whatever is well conceived is
clearly said... and the words to say it flow with ease

~~~
ComputerGuru
Ce qui est bien pensé se dit clairement ?

Edit: nevermind. I was way off.

Ce qui se conçoit bien s'énonce clairement, et les mots pour le dire arrivent
aisément.

------
jjguy
Einstein said it first:

If you can't explain it to a six year old, you don't understand it yourself.

[https://www.goodreads.com/quotes/19421-if-you-can-t-
explain-...](https://www.goodreads.com/quotes/19421-if-you-can-t-explain-it-
to-a-six-year-old)

------
nebulous1
I think some people (even lots of people) are pretty bad at explaining things,
even things they understand.

------
keithnz
I think you can't explain something in simple terms if you don't understand
it, is true, but the other way around isn't entirely true, or at least it's a
bit more fuzzy.

Often, it takes a lot of awareness of what are the common mental models /
mental blocks other people have when learning the concept you are trying to
communicate. You have to structure things as a series of strategic
progressions before tackling the most complicated form of something, all of
that is more the art of teaching ( which of course requires good understanding
)

Of course, if someone can do that, it's a brilliant proof they do understand
something.

If they can't do it, then it can leave you with doubt what someone else
understands. Which in Apples case may be considered entirely unacceptable.

------
leepowers
Feynman is an outlier, a very rare talent that could handle very complex maths
and also communicate these concepts in an approachable, charming, and laid-
back style. This is an in-born talent and also a skill that can be taught. But
communicating complex systems is a separate proficiency from understanding
those systems.

The main issue when explaining concepts (especially maths concepts) is
switching from one formal context to another, deciding what details to omit,
and determining what rules in both contexts should be treated as analogous.

Think of a translator. He/she/it needs proficiency in two languages to do a
proper translation. Lacking a second language precludes translation. But it
doesn't affect mastery of your native tongue.

------
jondubois
The term "simple terms" is subjective and depends on who the audience is.

A popular question to qualify for engineering job interviews is "describe in
simple terms what happens when a user accesses a website on the Internet" \-
The question doesn't give any info on who the target audience is so you never
know what level of detail you're supposed to go into. Because this is an
engineering question, I tend to go into more detail but after a certain level,
you can't really keep it simple because the reader has to understand what
things like cache are... Else you will spend 20 pages just writing
definitions.

------
timoth3y
There is no reason to believe this statement is true, and the article doesn’t
even try to make a case for it. It “feels” like it should be true, but the
discussion is really just asserting the statement.

Skeptic: “I understand X. I’ve spent years working on it, and I’m recognized
as an expert in the field. but I can’t explain X in simple terms.”

Believer: “Well, then you obviously don’t __really __understand it. Can you
prove to me that you do "

Being able to explain things in simple terms is a skill in and of itself. Many
people do not possess this particular skill, but that does not mean they are
unable to understand any subject.

------
CalChris
I interviewed a woman once who'd graduated from Caltech. She was massively
overqualified and a fine fit. So about 10 minutes into the interview I started
just having a nice conversation.

She'd gone to Caltech. That was on her resume. So I asked her if she'd ever
taken a class from Feynmann. That was actually unlikely but she had sat in on
a seminar with Feynmann once. She said he could explain the most difficult
material and that you would understand it. You would understand it walking
away and this would last about 15 minutes during which time you confuse
yourself.

------
NicoJuicy
Simple trick, you don't have to explain everything and use similar things (
when possible) in layman context. Explaining only cause and affect without the
method used can greatly simplify things when talking to non-programmers / non-
technical people

Eg. IP = A address like your home address. So the internet knows where to
search. We use zipcodes, the web uses numbers.

Then: I need to adjust a dns-record with our IP. Becomes, I will point the
website to our address.

If it's not obvious, then all my previous clients are lying ( just mentioning
it, cause it's possible)

------
flavio81
In science and engineering, there are some things that can't just be explained
in a small amount of simple words to laymen.

Sadly it's 2017 and the popularity of TEDTalks make the laymen think
otherwise.

------
nroach
I like the sentiment behind this article, but simplification (like lossy
compression) omits information for the cause of simplicity, leading to an
incomplete understanding.

Take for example legal concepts like securities law or environmental
regulation. Yes, you can "simplify" an explanation of the Securities Act or
the Paris Accord enough to fit them into a tweet, but you lose information
necessary to formulating a full understanding.

If you're trying to have an informed debate about policy adoption, the details
matter.

------
peterwwillis
I can simplify how a car engine works, but that doesn't mean I understand how
the air to fuel ratio is obtained.

Opposite example: Simplify how walking works, and make sure to include the
critical systems such as major muscle groups, stabilizers, vision, inner ear,
thigh/knee/pelvis/hip construction, the curved spine and its connection to the
head, and blood pressure flow/regulation.

~~~
outworlder
Still, you understand how it works. Is it enough to build one? Of course not.

You'd be missing a lot of experimental data that has been collected for
decades. You'd be missing the metallurgy, etc.

The basic principle is very simple. Maybe you could even build a low powered
version, given materials and time.

If you insist that understand how to obtain the proper air to fuel ratio is
required to understand how an internal combustion engine operates, then I'd
say we don't really understand anything at all. Can you mine and refine the
ore to create the allows it is made of? Can you program the ignition (or
alternatively, build a carburator)?

We all need to stop at some point.

~~~
peterwwillis
The funny thing is, I actually can mine ore, smelt it into iron and forge it.
That doesn't mean I can explain how that works (monoxides in a fuel binding to
oxides in iron ore to separate iron from slag, aligning grain and changing
durability by heat treating, etc). Maybe that doesn't matter if all you want
to do is produce pig iron, but if your specific engine design requires a
specific grade of alloy, now you need to fully understand metallurgy.

Take it a step further and the engine is built, but you need to make a
modification (forced induction, race fuel, etc). If you don't want your engine
to blow up, now you need to understand air/fuel mixture. Sure, I can do
something with a simplified understanding. But the lack of a complete
understanding will leave me with a blown-up engine.

Does it follow that if I understand metallurgy and internal combustion
engines, but can't simplify it, that I don't understand it? Of course not; the
entire premise was that I already understood it. Simplification does not show
you understand something. It can only provide a shallow, incomplete
understanding.

So you don't need to be able to simplify to understand. You need to understand
to understand. You need to simplify to provide a simplistic, shallow view.

------
jpmattia
If curious: This Feynman quote was more specifically about the spin-statistics
theorem.

[https://en.wikipedia.org/wiki/Spin%E2%80%93statistics_theore...](https://en.wikipedia.org/wiki/Spin%E2%80%93statistics_theorem)

And to be fair, it's pretty rough sledding even when you understand the
operators involved.

------
wolco
If you can explain something in simple terms you may not understand the
complex details.

If you hold a complex idea in your head translating that into English can be
difficult because part of the process is removing/altering information to fit
into existing notions. That is why buzzwords are popular they can take an idea
and put it in a relatable concepts for the masses.

------
zobzu
"or you just don't have good communication skills" It's a classic fallacy.
While it has some truth to it it's not the only single reason to decide if you
understand the subject or not.

In fact, "if you make this fallacy, you're a terrible human being" (which is
sarcasm here since this very statement includes the exact same fallacy)

------
bryanrasmussen
Or maybe you are just a really bad communicator.

~~~
sh87
Everyone was born a bad communicator. Some evolve into good ones some don't.
Its an acquired skill.

------
littlestymaar
IMHO, this statement never hold for Maths : since all math reasoning is just
the construction of a logical and symbolic proof based on a set of existing
theorems and the underlying axioms, it requires the student to :

1\. be familiar to the logical reasoning : what «implies» or even «for any x»
means. 2\. know the relevant set of theorem and axioms used in the
demonstration.

You could probably illustrate what a mathematical result implies in some real-
life example, but you won't be «explaining» it.

Quantum physics is a really good example of this, because it's not _that_
difficult to understand if you look at it with the mathematical PoV : it's
basically linear algebra in infinite dimension, you have vectors (in the space
of «functions of |R³») and linear applications on these vectors (with all
properties of such applications, like eigenvalues and eigenvectors), etc. But
if you try to «explain» it in simple terms, you're going to distort the
reality to fit in the macroscopic-scaled human representation of the world and
you'll probably say things that won't be true.

------
onikolas
Explaining something is compressing information and then transmitting it. As
we know, there are limits to how much we can losslessly compress information.

So, no, you cannot explain everything in simple terms. But you can find sweet
spots when trading brevity for accuracy.

------
naikrovek
This is so untrue. If true, beings that can't speak or write can never
understand anything.

I understood very early in life that if I cried I would be hit. I couldn't
talk, write, or communicate my understanding in any way, but I understood
clearly.

~~~
dredmorbius
Such beings have no social knowledge.

------
blakesterz
Kottke's one of the very few blogs I've been reading for what seems like
forever. He's still doing good work. Recently he's been trying membership,
which I've not seen on a site like his anywhere else.

------
hiq
A related maxim by Nicolas Boileau (1636 - 1711):

 _Whatever is well conceived is clearly said, And the words to say it flow
with ease._

 _Ce que l 'on conçoit bien s'énonce clairement, Et les mots pour le dire
arrivent aisément._

------
elnygren
"had I more time, I would've written a shorter letter".

Remember that "in simple terms" does not mean easy or over simplifying
something. To me it means making a to-the-point and jargon-free explanation.

------
imjustsaying
So people who can't teach their own language to foreigners in simple terms
don't understand their own language?

I've witnessed dozen of people try and spectacularly fail at teaching their
own language.

~~~
DrJokepu
Yes. Being able to speak a language intuitively is not the same as
understanding the mechanics of the grammar. For example, I don't believe that
many native English people have any idea how "accusative and infitive" works,
yet they use it every day.

------
Ngunyan
Really? In simple terms, explain how this works concisely.

------
blackkettle
If you don't understand something and/or cannot explain or describe it, should
you believe it? I think this is a very difficult question.

------
tutufan
Linear time suffix tree construction. You have 90 seconds. Go!

:-P

~~~
vlasev
Here [1] is not 1, but 3 different levels of complexity. Not 90 seconds though
:)

[1]: [https://stackoverflow.com/questions/9452701/ukkonens-
suffix-...](https://stackoverflow.com/questions/9452701/ukkonens-suffix-tree-
algorithm-in-plain-english/9513423#9513423)

------
stretchwithme
People know a lot of things they don't necessarily know how to explain. A lot
of people don't know how to teach.

------
matthberg
I think this is part of the beauty of simple.wikipedia.org. It is not only a
way for laymen to understand complicated things, yet proof of the research
being an actual understanding of the concept.

In the words of the xkcd on the subject, (check the title text):

"Actually, I think if all higher math professors had to write for the Simple
English Wikipedia for a year, we'd be in much better shape academically."
[https://xkcd.com/547/](https://xkcd.com/547/)

------
known
“If you can't explain it to a six year old, you don't understand it yourself”
―Albert Einstein

~~~
Scea91
Why is this quote used so often even when it is so ridiculously false?
Actually, did Einstein ever say that or is it just one of the fake quotes that
are attributed to him?

------
barce
Another way of putting this is: If you can't use lego blocks to build
something, then you don't understand it. But why would anyone want to recreate
Shakespeare using lego blocks, or recreate a motorcycle using lego blocks? I'm
sure a 5 year old would love it to pieces. I would rather make a reproduction
of a motorcycle with real metal.

------
std_throwaway
Keep it as simple as possible but don't try to make it more simple than it
actually is.

------
cryptozeus
"What I cannot create, I do not understand"

------
Tomminn
Corollary: All ideas worth understanding are simple.

------
danmaz74
Ok, so nobody understands quantum physics...

------
chrisallick
Someone explain cryptocurrency!

~~~
dredmorbius
[https://davidgerard.co.uk/blockchain/](https://davidgerard.co.uk/blockchain/)

------
twelvedogs
lol, apparently i don't understand anything

------
juandazapata
What is a monad?

~~~
Retra
It's a pattern of taking a series nested items and treating them as sequential
by implicitly passing the nesting context from one item to the next.

At least, that's the programmer's interpretation. Mathematically, they are
algebraic structures that can behave analogously to this in a number of
fashions.

------
draw_down
I think I've about gotten my fill of this piece of, uh, wisdom. It strikes me
as one of those things that sounds good but is less relevant than we'd like to
think.

------
williamle8300
Person A: Trump is colluding with Russia...

Person B: How?

Person A: You're a dummy! There's mountains of evidence!

Person B: Like...

Person A: You're killing the vibe brah.

