St. Agatho

Agatho · 678 – 681

A Sicilian monk whose letter to the Third Council of Constantinople helped end the Monothelite heresy, echoing Leo the Great's Tome.

Agatho was a Sicilian, reportedly a monk who became pope at an advanced age. His great achievement was his letter to the Third Council of Constantinople in 680-681, in which he clearly affirmed that Christ has two wills, divine and human, in harmony with one another. The council accepted his teaching and condemned Monothelitism, along with Pope Honorius I for his earlier ambiguity. Agatho's letter was consciously modeled on Leo the Great's Tome, and like Leo's, it carried the day. He died before the council concluded, but his doctrinal contribution was decisive.

The Second Tome

Agatho's letter to Constantinople did what Leo's Tome had done at Chalcedon two centuries earlier: it settled a Christological dispute with clarity and authority. The question was whether Christ had one will or two. Agatho said two, the council agreed, and Monothelitism was finished. It was one of the last great Christological debates, and the papacy was again at the center of the answer.