The Definition of Chalcedon

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 {meaning 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 {hypostasis}. They are not divided or cut into two persons, but are together the one and only and only-begotten Word {Logos} 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 {the Nicene Creed} has handed down to us.

Etext from http://www.creeds.net/ancient/chalcedon.htm.