Saying he’s too old and in too ill health to be the head of the church, Pope Benedict announced his resignation today, effective February 28.

The news came as a shock, since in the world of Catholics, when a pope is elected as the “Successor of St. Peter,” the church expects that he will remain in office until his death.

I’ve always wondered if a pope could resign. Apparently, the move isn’t precedent setting as Popes in the past have indeed resigned. Papal resignation is nothing new to the Vatican. According to Wikipedia, three popes have resigned over the long course of history, the most famous being Pope Celestine V, who stepped down after serving only five months after he issued a solemn decree declaring it permissible for a Pope to resign.

Pope Benedict’s resignation is valid under Canon Law, which cites the only conditions for the validity of the resignation are that it be made freely and be manifested properly. 

But why resign, rather than retire?