So you're in the middle of having a terrible argument with someone. You are absolutely convinced that you are right, and the other person's story doesn't make sense at all. You wonder how he cannot see your point of view. You've posed your views a number of times perfectly clearly and beyond a shadow of a doubt.
This is when you have to move from certainty to curiosity. In order to come to understand better the other person's side of the argument, you need to be curious and ask yourself how they can possible think that way. Put yourself in their shoes, understand their background and where he is coming from.
There's some kind of information that the other person has of which you are not aware. So rather than focussing on how irrational and crazy this person is, get curious and try to figure out what could possibly be the reason that their view can make any sense.
Certainty means hitting our head against the wall in hopeless and frustrating repetition. Curiosity opens the door and let's us enter into the other person's story.
The goal anyway is not so much attaining absolute certainty as getting closer to a mutual understanding that makes all parties involved feeling better.