Christology (from Greek Χριστός Khristós and -λογία, -logia) is the field of study within Christian theology which is primarily concerned with the nature and person of Jesus as recorded in the canonical Gospels and the epistles of the New Testament. Primary considerations include the relationship of Jesus' nature and person with the nature and person of God the Father. As such, Christology is concerned with the details of Jesus' ministry, his acts and teachings, to arrive at a clearer understanding of who he is in his person, and his role in salvation. A major component of the Christology of the Apostolic Age was that of Paul the Apostle. His central themes were the notion of the pre-existence of Christ and the worship of Christ as Kyrios (Greek: Lord).The pre-existence of Christ is considered a central theme of Christology. Proponents of Christ's deity argue the Old Testament has many cases of Christophany: ""The pre-existence of Christ is further substantiated by the many recorded Christophanies in the Bible."" Christophany is often considered a more accurate term than the term Theophany due to the belief that all the visible manifestations of God (or Yahweh) are in fact the preincarnate Christ. Many argue that the appearances of ""the Angel of the Lord"" in the Old Testament were the preincarnate Christ. ""Many understand the angel of the Lord as a true theophany. From the time of Justin on, the figure has been regarded as the preincarnate Logos.""Following the Apostolic Age, there was fierce and often politicized debate in the early church on many interrelated issues. Christology was a major focus of these debates, and was addressed at every one of the first seven ecumenical councils. The second through fourth of these councils are generally entitled ""Christological councils,"" with the latter three mainly elucidating what was taught in them and condemning incorrect interpretations. The Council of Chalcedon in 451 issued a formulation of the being of Christ — that of two natures, one human and one divine, ""united with neither confusion nor division."" This is called the doctrine of the hypostatic union, which is still held today among Eastern Orthodox, Roman Catholic, and many Protestant Christians, referred to collectively as Chalcedonian Christianity. Due to politically charged differences in the 4th century, schisms developed, and the first denominations (from the Latin, ""to take a new name"") formed.In the 13th century, Saint Thomas Aquinas provided the first systematic Christology that consistently resolved a number of the existing issues. In his Christology from above, Aquinas also championed the principle of perfection of Christ's human attributes. The Middle Ages also witnessed the emergence of the ""tender image of Jesus"" as a friend and a living source of love and comfort, rather than just the Kyrios image. According to Catholic theologian Karl Rahner, the purpose of modern Christology is to formulate the Christian belief that ""God became man and that God-made-man is the individual Jesus Christ"" in a manner that this statement can be understood consistently, without the confusions of past debates and mythologies.