The orthodox Christological doctrine that the one Person of Christ subsists in two complete natures — a fully divine nature and a fully human nature — united in the one Person without confusion, change, division, or separation. The doctrine was definitively formulated at the Council of Chalcedon (451) against the Christological heresies, in the Chalcedonian Definition: Christ is truly God and truly man... consubstantial with the Father according to the Godhead, and consubstantial with us according to the manhood; in all things like unto us, without sin... to be acknowledged in two natures, inconfusedly, unchangeably, indivisibly, inseparably; the distinction of natures being by no means taken away by the union, but rather the property of each nature being preserved, and concurring in one Person. The biblical foundation is the consistent witness to both the full deity and the full humanity of Christ in the one Person. Full deity: the Word was God (John 1:1); in Him dwells all the fulness of the Godhead bodily (Colossians 2:9); He is the brightness of God's glory and the express image of His person (Hebrews 1:3); Thomas confesses Him my Lord and my God (John 20:28). Full humanity: the Word was made flesh (John 1:14); He was born of a woman (Galatians 4:4); He grew in wisdom and stature (Luke 2:52); He hungered, thirsted, wearied, wept, suffered, and died (a true body and a reasonable soul); He was tempted in all points like as we are, yet without sin (Hebrews 4:15). The two natures are united in the one Person (not two persons; the heresy of Nestorianism) without being mixed or confused into a third hybrid nature (the heresy of Eutychianism / monophysitism), without the divine nature being changed, and without the natures being divided or separated. The patriarchal-Reformed reader holds the substantive Chalcedonian doctrine: Christ is one Person in two natures, fully God and fully man, the God-man (theanthropos), the one Mediator between God and men (1 Timothy 2:5).