February 2022  
  
Writing about something, even something you know well, usually shows you that
you didn't know it as well as you thought. Putting ideas into words is a
severe test. The first words you choose are usually wrong; you have to rewrite
sentences over and over  to get them exactly right. And your ideas won't just
be imprecise, but incomplete too. Half the ideas that end up in an essay will
be ones you thought of while you were writing it. Indeed, that's why I write
them.  
  
Once you publish something, the convention is that whatever you wrote was what
you thought before you wrote it. These were your ideas, and now you've
expressed them. But you know this isn't true. You know that putting your ideas
into words changed them. And not just the ideas you published. Presumably
there were others that turned out to be too broken to fix, and those you
discarded instead.  
  
It's not just having to commit your ideas to specific words that makes writing
so exacting. The real test is reading what you've written. You have to pretend
to be a neutral reader who knows nothing of what's in your head, only what you
wrote. When he reads what you wrote, does it seem correct? Does it seem
complete? If you make an effort, you can read your writing as if you were a
complete stranger, and when you do the news is usually bad. It takes me many
cycles before I can get an essay past the stranger. But the stranger is
rational, so you always can, if you ask him what he needs. If he's not
satisfied because you failed to mention x or didn't qualify some sentence
sufficiently, then you mention x or add more qualifications. Happy now? It may
cost you some nice sentences, but you have to resign yourself to that. You
just have to make them as good as you can and still satisfy the stranger.  
  
This much, I assume, won't be that controversial. I think it will accord with
the experience of anyone who has tried to write about anything nontrivial.
There may exist people whose thoughts are so perfectly formed that they just
flow straight into words. But I've never known anyone who could do this, and
if I met someone who said they could, it would seem evidence of their
limitations rather than their ability. Indeed, this is a trope in movies: the
guy who claims to have a plan for doing some difficult thing, and who when
questioned further, taps his head and says "It's all up here." Everyone
watching the movie knows what that means. At best the plan is vague and
incomplete. Very likely there's some undiscovered flaw that invalidates it
completely. At best it's a plan for a plan.  
  
In precisely defined domains it's possible to form complete ideas in your
head. People can play chess in their heads, for example. And mathematicians
can do some amount of math in their heads, though they don't seem to feel sure
of a proof over a certain length till they write it down. But this only seems
possible with ideas you can express in a formal language. [1] Arguably what
such people are doing is putting ideas into words in their heads. I can to
some extent write essays in my head. I'll sometimes think of a paragraph while
walking or lying in bed that survives nearly unchanged in the final version.
But really I'm writing when I do this. I'm doing the mental part of writing;
my fingers just aren't moving as I do it. [2]  
  
You can know a great deal about something without writing about it. Can you
ever know so much that you wouldn't learn more from trying to explain what you
know? I don't think so. I've written about at least two subjects I know well —
Lisp hacking and startups — and in both cases I learned a lot from writing
about them. In both cases there were things I didn't consciously realize till
I had to explain them. And I don't think my experience was anomalous. A great
deal of knowledge is unconscious, and experts have if anything a higher
proportion of unconscious knowledge than beginners.  
  
I'm not saying that writing is the best way to explore all ideas. If you have
ideas about architecture, presumably the best way to explore them is to build
actual buildings. What I'm saying is that however much you learn from
exploring ideas in other ways, you'll still learn new things from writing
about them.  
  
Putting ideas into words doesn't have to mean writing, of course. You can also
do it the old way, by talking. But in my experience, writing is the stricter
test. You have to commit to a single, optimal sequence of words. Less can go
unsaid when you don't have tone of voice to carry meaning. And you can focus
in a way that would seem excessive in conversation. I'll often spend 2 weeks
on an essay and reread drafts 50 times. If you did that in conversation it
would seem evidence of some kind of mental disorder. If you're lazy, of
course, writing and talking are equally useless. But if you want to push
yourself to get things right, writing is the steeper hill. [3]  
  
The reason I've spent so long establishing this rather obvious point is that
it leads to another that many people will find shocking. If writing down your
ideas always makes them more precise and more complete, then no one who hasn't
written about a topic has fully formed ideas about it. And someone who never
writes has no fully formed ideas about anything nontrivial.  
  
It feels to them as if they do, especially if they're not in the habit of
critically examining their own thinking. Ideas can feel complete. It's only
when you try to put them into words that you discover they're not. So if you
never subject your ideas to that test, you'll not only never have fully formed
ideas, but also never realize it.  
  
Putting ideas into words is certainly no guarantee that they'll be right. Far
from it. But though it's not a sufficient condition, it is a necessary one.  
  
  
  
  
  
  
  
  
  
**Notes**  
  
[1] Machinery and circuits are formal languages.  
  
[2] I thought of this sentence as I was walking down the street in Palo Alto.  
  
[3] There are two senses of talking to someone: a strict sense in which the
conversation is verbal, and a more general sense in which it can take any
form, including writing. In the limit case (e.g. Seneca's letters),
conversation in the latter sense becomes essay writing.  
  
It can be very useful to talk (in either sense) with other people as you're
writing something. But a verbal conversation will never be more exacting than
when you're talking about something you're writing.  
  
  
  
**Thanks** to Trevor Blackwell, Patrick Collison, and Robert Morris for
reading drafts of this.  
  

