You can prove anything you want by coldly logical reason- if you pick the proper postulates. We have ours and Cutie has his.
I believe in addition to postulates, a wealth of experience lets you steer the discussion and win the argument using logical reasoning. My father does this all the time. No matter where we start a topic, in the end, the story is the same. I am forced to agree with him because the arguments are rational and said in a logical way.