People often leave information out of their writing that I think a reader would want or need to know (we're assuming here a reader who's somewhat interesting and at least potentially interested in what one has to say). I'm a person and I do this too, so I made a checklist for myself. It would be burdensome to always feel the requirement to put everything in, would make writing a chore. But I'm certain that when I leave things out I'm not always doing so by choice. So the goal here is to make sure that my decision to leave things out is somewhat conscious.
(1) I'm explaining my idea fully, dotting i's, crossing t's, italicizing, repeating everything that's counterintuitive or unexpected to make sure it's not misread, am doing my best to guarantee that the people I'm trying to reach will have to be really negligent to misunderstand.
(2) As before, except I'm not all that sure what my idea is; it may only be a sense of something, not a fully thought-through thought. But I'm being as clear and intelligible as possible about where I'm confused or ambivalent or tentative, where I'm being vague ("I realize that this is vague, but…"), where I'm not sure what the right word is, where I'm being incomplete.
(3) I'm doing either 1 or 2 except I'm a bit worried about letting the readers in on the fact that I think they're ignorant or not all that smart, so I leave out some of the italics and repetitions, or at least try to be a bit manipulative or in disguise when I'm actually saying something that I said a few paragraphs earlier but didn't trust them to get the first time.
(4) I'm leaving stuff out that I assume the reader already knows.
(5) I'm leaving stuff out because I don't have time or space (in which case, where I've got room or am allowed to, I write "I'm leaving this out").
(6) I'm leaving stuff out because I think the readers will get the points more strongly - and will retain the points - if they do some of the figuring out themselves. Also, some jokes are funnier when the meaning of punch lines dawns on the reader rather than hitting her immediately.
(7) I'm leaving things out to avoid hurting people's feelings, but hoping I've said enough that at least there's a chance they'll get the basic intellectual point anyway without having to directly confront the fact that I've told them they were wrong and that they misread and they were throwing a fit or were being snarky or were trying to bully me etc.
(8) I'm writing aphoristically, I'm writing playfully, I'm writing poetry, I'm writing notes mainly for my own benefit, I'm tossing words around to see what happens, I'm being deliberately half-baked and maybe will say something new and surprising while the pressure's off, etc.
(9) I want to get stuff down on paper or online quickly, and we can all wait till later to figure out what I could be saying.
Of course, I can combine different modes in the same post or piece, be super explanatory in one section and fast and funny in another, in some spots I can put in double meanings and cross-references and ironies that are there for those who get them but aren't waving a flag at people who don't. But again, the idea is to be conscious of when I'm doing this, so either I've still supplied enough for the reader who doesn't get all that's going on to still retain the thread, or I'm consciously taking the risk of losing or challenging some readers, willing to lose some in order to challenge others and give yet others a chuckle.
By the way, I'm leaving a lot of info out of this post since I'm about to go to sleep and I'm hoping you'll have no trouble coming up with your own examples of 1 through 9. I think my "
Austral-Romanian Empire" post is an example of 2 combined with 3, and my intro and first post to
my old Thomas Kuhn thread on ilX is an attempt at 1 - though it does assume fundamentally smart readers who I expect will nonetheless need a lot of information before they can find their feet. (And the result seemed to be otherwise smart readers not even knowing where their feet were, much less the ground.)