Christology (from Greek Χριστός Khristós and -λογία, -logia), literally 'the understanding of Christ,' is the study of the nature (person) and work (role in salvation) of Jesus Christ. It studies Jesus Christ's humanity and divinity, and the relation between these two aspects; and the role he plays in salvation. The earliest Christian writings gave several titles to Jesus, such as Son of Man, Son of God, Messiah, and Kyrios, which were all derived from the Hebrew scriptures. These terms centered around two themes, namely 'Jesus as a preexistent figure who becomes human and then returns to God,' and 'Jesus as a creature elected and 'adopted' by God.' From the second to the fifth centuries, the relation of the human and divine nature of Christ was a major focus of debates in the early church and at the first seven ecumenical councils. The Council of Chalcedon in 451 issued a formulation of the hypostatic union of the two natures of Christ, one human and one divine, 'united with neither confusion nor division'. Most of the major branches of Western Christianity and Eastern Orthodoxy subscribe to this formulation, while many branches of Oriental Orthodox Churches reject it, subscribing to miaphysitism. Christology (from Greek Χριστός Khristós and -λογία, -logia), literally 'the understanding of Christ,' is the study of the nature (person) and work (role in salvation) of Jesus Christ. It studies Jesus Christ's humanity and divinity, and the relation between these two aspects; and the role he plays in salvation. 'Ontological Christology' analyzes the nature or being of Jesus Christ. 'Functional Christology' analyzes the works of Jesus Christ, while 'soteriological Christology' analyzes the 'salvific' standpoints of Christology. Several approaches can be distinguished within Christology. The term 'Christology from above' or 'high Christology' refers to approaches that include aspects of divinity, such as Lord and Son of God, and the idea of the pre-existence of Christ as the Logos (the Word), as expressed in the prologue to the Gospel of John. These approaches interpret the works of Christ in terms of his divinity. According to Pannenberg, Christology from above 'was far more common in the ancient Church, beginning with Ignatius of Antioch and the second century Apologists.' The term 'Christology from below' or 'low Christology' refers to approaches that begin with the human aspects and the ministry of Jesus (including the miracles, parables, etc.) and move towards his divinity and the mystery of incarnation. A basic Christological teaching is that the person of Jesus Christ is both human and divine. The human and divine natures of Jesus Christ apparently (prosopic) form a duality, as they coexist within one person (hypostasis). There are no direct discussions in the New Testament regarding the dual nature of the Person of Christ as both divine and human, and since the early days of Christianity, theologians have debated various approaches to the understanding of these natures, at times resulting in ecumenical councils, and schisms.