Commenter Ian wrote the following, and I thought it worth sharing in a blog post:
Surety is cheap. The Pharisees were sure they were right, the 9/11 terrorists were sure they were right, as they gave their lives for what they were sure of, the Nazis were sure they were right and the world would be better with the Jews exterminated. Being sure is not difficult, and it is not a sign of being right. Those who are most sure are usually most dangerous. Run from anyone who promises certainty.
That some branches of Christianity try to make a virtue out of certainty, is a big warning sign of their desire to control and abuse you.