In this election season, many of us get into heated political conversations. Or maybe it’s about public policy (such as climate change). Or science education (evolution). Or religion (end times). One frustrating recent example is atheist Bob Price explaining how he’s an enthusiastic Trump supporter.
You might ignore your better instincts and jump into such an argument, but you’ll probably get nowhere. The thing that gives me the most enduring frustration is not being able to say “I told you so” once the evidence is in. That is, when things play out just like you said they would—whether ten days have passed or ten years—you never even get the minimal satisfaction of hearing your antagonist admit that they were wrong. They conform to the new data without that unpleasant I-was-wrong phase.
The point is not to show how smart you are or your superiority (though that might please the ego) but for the antagonist to learn something to create a small hope that they will be less likely to make this kind of mistake again.
Let me add two hopefully obvious clarifications: (1) sometimes the antagonist does indeed admit their error (it’s just that this is rare) and (2) this goes both ways, and it might be us eating the humble pie and learning the lesson.
Commit to a public declaration
So how can we improve our chances of eventual satisfaction? Let’s say that the topic is rabbit overpopulation, and your antagonist is in favor of the upcoming ballot initiative to release radioactive super-weasels to control the rabbit problem.
You list the problems with this approach but your friend disagrees. Then the initiative passes, the weasels are released, and the environmental catastrophe (and untouched rabbit population) plays out like you predicted. When you confront your friend with this, he agrees that it was a disastrous project but denies specifics of both his prior position and your prediction.
The answer is for you to write a shared Public Declaration. This is a short statement summarizing the facts that clearly states what one of you think will or won’t happen and the time frame. It should be unambiguous so that an objective third party could determine who was right. (Of course, you could both be partly right. Or partly wrong.)
Let’s go back to the rabbit overpopulation problem and imagine that it ended with your writing this:

Sigmund Freud and I disagree on the best approach to the rabbit overpopulation problem. Sigmund advocates the radioactive weasels proposal in Initiative 7 on the November, 2016 ballot. I think it will be a terrible idea.
Prediction: I predict that the weasels will (1) have little impact on the rabbit population and (2) have the side effect of endangering the populations of other animals like birds. This is the position of the Natural Resources Defense Council (NRDC), which has come out against Initiative 7.
Test: Check with the NRDC one year after the proposal has been implemented to see if things turned out how I predicted.
(signed) Friedrich Nietzsche

Here’s what’s good about this statement.

• It’s specific about the claim: you referred to Initiative 7 on the November ballot, and you predict that if implemented, “the weasels will (1) have little impact on the rabbit population and (2) have the side effect of endangering the populations of other animals like birds.” There’s no need to also summarize your opponent’s position because he simply thinks that you’re wrong.
• It’s clear on the time frame: judgment day is “one year after the proposal has been implemented.”
• It defines an objective test: use the NRDC’s analysis after the proposal has had time to work. This could be a weakness of this public declaration if the NRDC is seen as biased. Another option might be to predict an editorial confirming your position. It works as long as your opponent agrees on the test. It’s tempting to imagine that “everyone” on this future date will just know who was right, but the lack of a clear test would weaken such a statement.
• It’s a shared statement. This project works best when you work on it and sign it together.
• Recording your position for posterity is satisfying, which is better than just walking away frustrated and angry.

Be as specific as possible. Things that are clear and obvious in your mind now could be forgotten by the time the prediction must be evaluated. (Contrast this with the vague and unspecific claims made by biblical prophecies.) Imagine the future judgment day and give yourself a clear and unambiguous statement to work with.
By writing the statement together, each party should be proud, rather than reluctant, to sign it and commit to it.
How can someone forget so important a position?
While you’re arguing with someone, the argument and your position are very, very clear in your mind. (Well, you think things are clear. Simply writing down the issue may reveal a misunderstanding that could advance the discussion.)
While the declaration could prevent your antagonist from lying about their former position once it’s been proven wrong, I think simple forgetfulness is the bigger issue. The Challenger memory experiment makes clear the difference between vivid and accurate memories—just because you have a clear memory of a past incident doesn’t mean that memory is correct. (I write more about this experiment here.)
Implementation
The idea could play out in different ways. This could be as casual as notes on the back of a napkin or cardboard coaster, though something this informal might get lost. It could wind up on a Facebook post (use a consistent phrase, like “public declaration,” so that you can search for it on judgment day). Or maybe there’s a single site, PublicDeclarations.com, that could give a simple template for those who want to boldly plant their flag.
This could work for several kinds of claims.

• If-then claims such as, “If same-sex marriage is legalized in the U.S., then X will happen” or “If Hillary is elected, then X will happen.”
• An even simpler claim is, “X will happen,” such as the predictions about the end of the world by John Hagee, Hal Lindsey, and Harold Camping. Another example: “Biologists will realize that evolution doesn’t explain life.”

Since arguments usually distill down to a simple “Yes, it will” vs. “No, it won’t” dichotomy, public declarations could have wide applicability.
What do you think?

We survive by virtue of people extending themselves,
welcoming the young, showing sympathy for the suffering,
taking pleasure in each other’s good fortune.
We are here for a brief time.
We would like our stay to mean something.
Do the right thing.
Travel light.
Be sweet.
– Garrison Keillor

Image credit: Jonathan Baker-Bates, flickr, CC