Subsequently to Ephesus there was a development of doctrine concerning our Lord. Twenty years after the close of the Council of Ephesus it was taught at Chalcedon—against the Monophysites who maintained that the Human Nature in Christ was swallowed up in the Divine as a drop of water in a cup of wine—that the two Natures remain distinct in the One Lord Jesus Christ. Christ our Lord is truly Man. He possesses a Human Nature which He assumed of Mary His Mother, perfect in all that belongs properly to human nature as such:
"He is like us in all things, sin only excepted." From this it follows (as was afterwards defined against the Monothelites) that our Lord possesses two Wills—a Human Will belonging to His Human Nature as well as His Divine Will as God. The doctrine of the two Wills in Christ is a development from the doctrine of the two Natures. Similarly, the doctrine of the Immaculate Conception is the development or unfolding of the doctrine that Mary is the Second Eve, in which it lay hidden as a germ; just as the doctrine of Original Sin is itself a development that may be deduced from the doctrine laid down by St. Paul that our Lord is the Second Adam, the Redeemer of all men.