ex cathedra

Ex cathedra is a Latin phrase, meaning not "from the cathedral," but "from the chair." The phrase does have religious origins though: it was originally applied to decisions made by Popes from their thrones. According to Roman Catholic doctrine, a Pope speaking ex cathedra on issues of faith or morals is infallible. In general use, the phrase has come to be used with regard to statements made by people in positions of authority, and it is often used ironically to describe someone speaking with overbearing or unwarranted self-certainty.