Catholicism is the practice of the Catholic religion and following the teachings that this religion hands out. This includes confession, which is very important in order to purge sins from the soul and receive god's forgiveness, as well as other religious practices. Priests provide guidance and teaching in the tenets of the faith, and they help guide Catholics to live a better and more devout life that places them closer to god.
We don't call a man mad who believes that he eats God, but we do the one who says he is Jesus Christ