"This guest post, by the author of Word Up! How to Write Powerful Sentences and Paragraph (And Everything You Build from Them) , previously appeared on How to Write Everything on Oct. 2, 2013.
When I visit Lan Su, the Chinese Garden here in Portland, Oregon, I like to stop at Knowing the Fish Pavilion, which overlooks the end of the lily pond where clusters of fat koi—orange, yellow, black, and white—navigate the shallows like so many finned watermelons. Tour guides always stop at this pavilion and tell the story of two scholars walking along the bridge over the Hao River.
“Look at the fish swimming about,” says Zhuangzi. “See how happy they are.”
“How do you know that they are happy?” says Huizi. “You are not a fish.”
“How do you know that I do not know?” says Zhuangzi. “You are not I.” 
This story—at least this rendition of the story  —reminds us not to presume that others (fish or people) experience the world the same way we do. Just as Zhuangzi can’t presume to know what the fish feel, Huizi can’t presume to know what Zhuangzi knows. A German saying that I learned as exchange student captures the truism this way: “Du kannst nicht aus deiner Haut heraus.” You can’t get out of your own skin.
At least that’s the lesson I draw from this story about the fish and the scholars. You may take away a different lesson. I shouldn’t presume…
But I do presume. I do it all the time. I automatically conjure readers who see in my words the same thing I see. While I write, I imagine readers nodding in agreement as they take in my post, proposal, or presentation. Exactly! I hear them say, as if they were I.
How happy we are! Zhuangzi hears the fish say, as if they were he.
Our readers, ourselves. To conflate the two is to fall into the Presumption Trap. How can writers steer clear?
One classic technique is to include a concession paragraph, a paragraph that acknowledges the validity of certain viewpoints at odds with your main argument. (Not every kind of writing makes an argument, but business writing often does. If you’re writing to persuade, you’re making an argument.) Typically, a concession paragraph directly follows an introductory paragraph that has stated the argument. A writer who follows this structure essentially says, right up front, You might disagree with me, and I can understand why.
But concentrating your concessions in your second paragraph isn’t the only way to acknowledge opposing views. Frances M. Perry, the author of the 1906 textbook An Introductory Course in Argumentation, calls for writers to think like debaters:
We writers—whether we’re building an argument or documenting a procedure or creating a lookup table—must give up the fantasy of easy acceptance if we want to avoid the Presumption Trap. We must suspend the illusion of like-mindedness, of oneness with our readers. We must detach ourselves and acknowledge that readers see what we write in their own ways. We can presume only one thing about readers: that we can’t presume anything.
They are not we.
I wonder what the fish feel? a detached Zhuangzi might have said. Perhaps they are not happy. Perhaps they are hungry or tired or afraid. Perhaps they have some fishy feeling that you and I could never experience. Of course, if he had said that, the “Happiness of Fish” story would never have survived over 2000 years for tour guides to tell. Zhuangzi knew what he was doing when he led his companion into the Presumption Trap. 
I fell into the Trap the first time I wrote a guest post. I wrote it with a sympathetic audience in mind. It didn’t occur to me that some readers would call me out for gaps in my knowledge and for having the audacity to give language-usage advice in the first place. I learned from my stumble. I learned that I still had a lot to learn about language. And I learned that knowing about a trap doesn’t keep you out of it.
In a recent online conversation about one of his blog posts, technical-communication blogger Mark Baker describes the Presumption Trap this way:
One of the things I have learned in a career as a writer is that people often interpret things they read in terms of the thread that is already running in their heads. In fact, we not only read that way, we write that way—sort of unconsciously assuming that our readers will be reading with the same bee in their bonnets that we have in ours. 
If Baker had been channeling Zhuangzi, he might have said, “How can we know that our readers have the same bee in their bonnets that we have in ours? We are not they.”
Baker does not suggest, though, as Perry did over a century ago, that writers should aim to build up an irrefragable argument. Instead, he points out that the Web has changed writing. Baker says that the Web enables us to “discuss and clarify our thoughts interactively, as we are doing now, rather than forcing us to try to anticipate and avoid every possible misunderstanding of our argument.”
Both Perry and Baker have legitimate points. Perry—to whom “early adopter” would have meant someone who used a typewriter—argues that, as much as possible, writers should anticipate misunderstandings and address objections before they publish. Baker argues that, in the Web era, we no longer have to.
Imagine Perry and Baker walking together, along a river, perhaps. They would debate. She would concede points to him, and he to her. In the end, they would arrive on common ground: savvy writers do what they can to avoid the Presumption Trap. On this point, Perry and Baker would agree.
Or would they?
 Does “You are not I” sound funny to you? Would you say “You are not me” instead? Until I researched this question, I presumed that only one phrasing could be correct. I now know that both have been widely considered acceptable since the first half of the eighteenth century. One of the most respected grammarians of our time, Bryan A. Garner, kicks off his long discussion of this topic like this: “Generally, of course, the nominative pronoun … is the complement of the linking verb . But it is me and it’s me are fully acceptable, especially in informal contexts.” For the rest of this discussion, see the entry “it is I; it is me” in Garner’s Modern American Usage, 3rd ed. (Oxford: Oxford University Press, 2009), 485-6.
 Before writing this post, I presumed that the “Happiness of Fish” story I heard from Lan Su tour guides was the whole story. I now know that the original story, written some 2400 years ago, ends with another round in the scholars’ conversation. For the whole story, and one blogger’s contemporary take on it, see Scott Bradley, “ The Happiness of Fish ,” The Rambling Taoists blog, May 4, 2010.
 Until my husband reviewed a draft of this post, I presumed that the characters in the “Happiness of Fish” story were fictional. I now know that Zhuangzi (Master Zhuang) was not only a character in this story but also its author, the influential Taoist philosopher who lived around the 4th century BCE.
 To review the discussion, see my post “ To Each Their Own ” on Tom Johnson’s I’d Rather Be Writing blog, April 16, 2011.
 Mark Baker in a comment following his post “ Why Is Writing the Only Profession Untouched by Its Tools? ,” Every Page Is Page One blog, July 29, 2013.
This post first appeared September 18, 2013, in my TechWhirl column, “ Word Wise .”