(VATICAN CITY) — He slipped it in at the end of his speech, and said it so quickly and softly it almost sounded like an afterthought.

But in pledging his “unconditional reverence and obedience” to the next pope, Benedict XVI took a critical step toward ensuring that his decision to break with 600 years of tradition and retire as pope doesn’t create a schism within the church.

It was also a very personal expression of one of the tenets of Christian tradition that dates back to Jesus’ crucifixion: obedience to a higher authority....