Speaking with reporters last week, Pope Francis acknowledgedthat the Catholic Church is confronted not just with a crisis of widespread allegations of sexual assault and abuse of minors, but also the rape and even “a kind of sexual slavery” of nuns.

This statement was not technically news. Many already knew of these long-standing allegations of such horrific abuses of power.

What was new, and what some might consider a grave sin on the part of the pope, was not his silence but his public recognition of the problem.

We know all too well how long Catholic authorities have sought to keep priests’ sexual sins quiet. Only recently, because of the brave children and nuns who have come forward, has the depth of sexual abuse in the church been acknowledged as a crisis that must be addressed.

But why has scandal been systematically silenced in the church for so long? One answer lies in the medieval church's doctrine on scandal.