Rising out of the Nestorian schism were more Christological conflicts over the relationship between Christ’s humanity and divinity. Eutyches, an opponent of Nestorius, went too far in the opposite direction, claiming that Christ’s human and divine natures were fused into one single nature. His human nature, Eutyches claimed, was “dissolved like a drop of honey in the sea.”
This heretical understanding, according to Clemmons, turned Christ into a “third thing” or a “kind of monster” rather than the Catholic understanding of Christ as “one Person” with “complete and true humanity and complete and true divinity.”
To combat Eutyches’ error, Pope Leo wrote a letter to Flavian I, the archbishop of Constantinople, which clarified the hypostatic union of Christ’s distinct human nature and distinct divine nature. The letter, which became known as “Leo’s Tome,” is the pontiff’s most famous work and set the stage for defining Christological doctrines at the Council of Chalcedon in 451.
“Both natures retain their own proper character without loss: and as the form of God did not do away with the form of a slave, so the form of a slave did not impair the form of God,” Pope Leo wrote in the letter.
“From the mother of the Lord was received nature, not faultiness: nor in the Lord Jesus Christ, born of the Virgin’s womb, does the wonderfulness of his birth make his nature unlike ours,” the letter continued. “For he who is true God is also true man: and in this union there is no lie, since the humility of manhood and the loftiness of the Godhead both meet there.”
In emphasizing the fullness of Christ’s human nature in the letter, Leo cites the genealogy of Christ listed in the Scripture, along with his human experiences, particularly suffering and death on the cross: “Let [Eutyches] not disbelieve [Christ is a] man with a body like ours, since he acknowledges [Christ] to have been able to suffer: seeing that the denial of his true flesh is also the denial of his bodily suffering.”