Council of Chalcedon
In A.D. 451, the Council of Chalcedon determined that Christ is God, that Christ is man, that Christ is one person (not two), and that the deity and humanity of Christ are not blurred. This Council thereby condemned the heresies of Monophysitism or Eutychianism.
In response to controversy and debate regarding which books are Scripture, the Council definitively listed 27 books of the New Testament and 46 books of the Old testament: 73 books of the Bible. See Bible