The two questions

The next four chapters are the method, and the method starts with two questions that take about a second each and end most arguments before they start.

Is it true? Not "am I sure". Chapter 3 is about why sure is worthless. Is there a record? A calendar, a message, a receipt, a photo? If there is, the question is answered by looking, not by arguing, and looking is chapter 21's job. If there isn't, and the fact is a memory or an impression, the honest answer is "I don't know", and a thing neither of you can know isn't a thing either of you can win.

Does it matter? Suppose you're right. Suppose the plumber came on Tuesday and you could prove it this second. What changes? If the answer is "nothing, but I'd have been right", it doesn't matter, and the argument is about the score. If the answer is "the insurance claim has the wrong date on it", it matters, and it's a job, not an argument. "Let's check the date before we send the form" is a sentence about a job.

Either no, drop it. If it's not true, or you can't know, or it doesn't matter, the argument has no content and the only thing left in it is the win. Drop it, out loud, in one of the sentences in chapter 21.

Both yes, chapter 22. If it's true, or checkable, and it matters, then you have a real disagreement about a real thing, and chapter 22 is about how to have that, and it doesn't look like the plumber.

Ask them silently. The questions are for you, at the table, in the second before you reach for your phone. They're not to be asked of your partner as a challenge. "Does it even matter?" said with an edge is a move in the spiral. Asked of yourself, it's the exit.

Write them on a card for a fortnight. Two questions on a card in your wallet, or on the fridge, or as the lock screen. Not because you'll forget them, but because the urge to correct is faster than memory, and a card in view is faster than the urge.

Expect most arguments to fail the second question. In my observation, if the list from chapter 1 is honest, nine in ten of the facts on it don't matter by this test, and the tenth is a job. That's not a sign that your disagreements are trivial. It's a sign that the arguments were never about the disagreements.