Christian ethics is defined as the moral principles governing the outlook and conduct of those individuals who adhere to the teachings of Jesus of Nazareth, who lived in the first century CE. The source for these teachings can be found in the Christian New Testament as well as parts of the Jewish Pentateuch. Christian ethics is based on the concept of "obedient love," or the idea of faith working through love. It also incorporates to some extent the tenet of "original sin" and the inherent fragility of human free will, and stresses the requirement of divine mercy and grace to overcome human vices and embody human virtues.
Christianity espouses that Jesus is the Jewish Messiah as prophesied in the Christian Old Testament, and is therefore considered the Savior of humanity. As a result, he is also known as Jesus Christ, or simply Christ, derived from the Greek word for "anointed." In most Christian denominations, Jesus is believed to be God in human form, and/or the son of God, who died and was resurrected. Based on these beliefs, the teachings of Jesus are considered the ultimate authority for human morality and conduct.
One of the best-known set of teachings forming the foundation of Christian ethics is the Sermon on the Mount, found in the gospels of Matthew and Luke. The discourse includes the Eight Beatitudes, or blessings, in which the virtues of humility, piety, mercy and compassion are extolled and subsequently assured of reward. Additionally, it is proposed that sinful human action, such as adultery or murder, actually commences in a person's thoughts in the form of lust or anger, and one who carries those thoughts also bears the commensurate guilt. The Sermon also provides the foundation for the concept of the Great Commission, or the duty to spread Christian teachings to all nations through evangelism and baptism, which are derived from the "light of the world" and "salt of the earth" parables.
In the accounts of Mark and Matthew, the greatest fulfillment of God's plan as taught in Christian morality is love for God (with the entirety of one's heart, soul and mind) as well as the love for one's neighbor (as one would love oneself). As a result, Christian ethics emphasizes acts of kindness and charitable giving. As is stated in the account of Luke, a good Christian should sell one's possessions in order to help someone else, and give one's cloak to someone who has none.
Other aspects of Christian ethics include the nature of one's relationship to earthly authority, which can be found in the teaching "Render unto Caesar." This concept demands that Christians pay taxes and submit to secular sovereignty, and provides the biblical basis for the separation of Church and State.
The teachings of Paul are another source from which Christian ethics have been drawn. Paul, a former Pharisee who converted to Christianity, espoused the doctrine of the "Fall of Man" and the spiritual implications for subsequent generations. St. Irenaeus of Lyon, and later St. Augustine of Hippo, expanded this idea into the concept of "original sin" in the second and fourth centuries, respectively.
Paul also was a strong advocate of a "covenantal," or guaranteed, relationship between God and all the nations, not just the Jews. Therefore, equality and ecumenicalism are strong components of Christian ethics.
The Apostolic Conference of Jerusalem in 50 CE set forth additional principles, including that of the abrogation of Jewish Law and the supersession of Christian ethics. Supersessionism, or replacement theology, teaches that adherence to the Christian New Testament is the completion or fulfillment of God's covenant with the Jews. The Apostolic Conference held that Gentiles who converted to Christianity were not obliged to observe Mosaic Law, including male circumcision. However, it was decreed that Christians would be commanded to abide by certain Jewish prohibitions, particularly those against idolatry and the consumption of blood.
Although traditionally the realm of Christian ethics was confined to one's private life and personal conduct, historically it has been the driving force behind the interactions of Christianity and other cultures and religions on issues ranging from armed conflict, slavery and racism to sexual and gender issues. Today, with one-third of the world's population counted as adherents, it is a strong component of government policies and political platforms in countries around the world. For example, in the United States, Christians have shaped the pro-life movement in a major opposition force to the country's policies on abortion, which they consider to be murder.