Definition of Chalcedon (451 AD)
@Following, then, the holy fathers, we unite in teaching all men to
confess the one and only Son, our Lord Jesus Christ. This selfsame
one is perfect both in deity and in humanness; this selfsame one is
also actually God and actually man, with a rational soul
human soul> and a body. He is of the same reality as God as far as
his deity is concerned and of the same reality as we ourselves as
far as his humanness is concerned; thus like us in all respects, sin
only excepted. Before time began he was begotten of the Father, in
respect of his deity, and now in these "last days," for us and behalf
of our salvation, this selfsame one was born of Mary the virgin, who
is God-bearer in respect of his humanness.
@We also teach that we apprehend this one and only Christ-Son, Lord,
only-begotten -- in two natures; and we do this without confusing
the two natures, without transmuting one nature into the other,
without dividing them into two separate categories, without con-
trasting them according to area or function. The distinctiveness
of each nature is not nullified by the union. Instead, the
"properties" of each nature are conserved and both natures concur
in one "person" and in one reality . They are not
divided or cut into two persons, but are together the one and
only and only-begotten Word of God, the Lord Jesus Christ.
Thus have the prophets of old testified; thus the Lord Jesus
Christ himself taught us; thus the Symbol of Fathers
Creed> has handed down to us.