Tamsen Webster explains why assumptions aren't agreements. When you disagree, stop arguing about who's right and instead explicitly define what you're talking about, then verify you both mean the same thing.
An assumption isn't an agreement. It just looks like one until it breaks. What you don't wanna do is try to win the argument in the moment about whose view of reality is right. You can only agree on something once it's been defined. Make the piece of reality that you need or that you're talking about explicit, and then check to see whether or not it's shared.
