Council of Chalcedon

Historical context

Convened against Eutychian monophysitism, which collapsed Christ's two natures into one.

Major decisions

• Defined Christ as one Person in two natures, divine and human.
• Adopted the Chalcedonian Definition, drawing on Leo's Tome.

Canons

30 canons including the disputed Canon 28 on Constantinople's rank.

Long-term impact

Set the boundaries of Chalcedonian Christianity; Oriental Orthodox churches separate.