Christian theology

====Monotheism====
[[File:Christ in Gethsemane.jpg|thumb|upright|''Christ in Gethsemane'', [[Heinrich Hofmann (painter)|Heinrich Hofmann]], 1890]]
Some Christians believe that the God worshiped by the Hebrew people of the pre-Christian era had always revealed himself as he did through [[Jesus]]; but that this was never obvious until Jesus was born (see [[John 1]]). Also, though the [[Angel of the Lord]] spoke to the Patriarchs, revealing God to them, some believe it has always been only through the [[Holy Spirit|Spirit of God]] granting them understanding, that men have been able to perceive later that God himself had visited them.

This belief gradually developed into the modern formulation of the [[Trinity]], which is the doctrine that God is a single entity ([[Yahweh]]), but that there is a trinity in God's single being, the meaning of which has always been debated. This mysterious "Trinity" has been described as [[Hypostasis (religion)|hypostases]] in the [[Greek language]] ([[Consubstantial|subsistences]] in [[Latin]]), and "persons" in English. Nonetheless, Christians stress that they only believe in one God.

Most Christian churches teach the Trinity, as opposed to Unitarian monotheistic beliefs. Historically, most Christian churches have taught that the nature of God is a [[Sacred mysteries|mystery]], something that must be revealed by [[special revelation]] rather than deduced through [[general revelation]].

Christian orthodox traditions (Catholic, Eastern Orthodox, and Protestant) follow this idea, which was codified in 381 and reached its full development through the work of the [[Cappadocian Fathers]]. They consider God to be a [[Wiktionary:triune|triune]] entity, called the Trinity, comprising the three "Persons"; [[God the Father]], [[God the Son]], and [[God the Holy Spirit]], described as being "of the same substance" ({{lang|grc|[[ousia|ὁμοούσιος]]}}). The true nature of an infinite God, however, is commonly described as beyond definition, and the word 'person' is an imperfect expression of the idea.

Some critics contend that because of the adoption of a tripartite conception of deity, Christianity is a form of [[tritheism]] or [[polytheism]]. This concept dates from [[Arianism|Arian]] teachings which claimed that Jesus, having appeared later in the Bible than his Father, had to be a secondary, lesser, and therefore distinct god. For [[Jews]] and [[Muslims]], the idea of God as a trinity is [[heresy|heretical]]– it is considered akin to [[polytheism]]. Christians overwhelmingly assert that monotheism is central to the Christian faith, as the very [[Nicene Creed]] (among others) which gives the orthodox Christian definition of the Trinity does begin with: "I believe in one God".

In the 3rd century, [[Tertullian]] claimed that God exists as the Father, the Son, and the Holy Spirit—the three personae of one and the same substance.<ref name=UCP>''Critical Terms for Religious Studies.'' Chicago: The University of Chicago Press, 1998. ''Credo Reference''. 27 July 2009</ref> To trinitarian Christians God the Father is not at all a separate god from God the Son (of whom [[Jesus]] is the incarnation) and the Holy Spirit, the other ''[[Hypostasis (religion)|hypostases]]'' (Persons) of the [[Godhead (Christianity)|Christian Godhead]].<ref name=UCP/> According to the Nicene Creed, the Son (Jesus Christ) is "eternally begotten of the Father", indicating that their divine Father-Son relationship is not tied to an event within time or human history.

In [[Christianity]], the [[doctrine]] of the Trinity states that God is one being who exists, simultaneously and [[eternity|eternally]], as a [[perichoresis|mutual indwelling]] of three Persons: the Father, the Son (incarnate as Jesus), and the Holy Spirit (or Holy Ghost). Since earliest Christianity, one's salvation has been very closely related to the concept of a triune God, although the Trinitarian doctrine was not formalized until the 4th century. At that time, the [[Constantine I and Christianity|Emperor Constantine]] convoked the [[First Council of Nicaea]], to which all bishops of the empire were invited to attend. [[Pope Sylvester I]] did not attend but sent his [[Papal legate|legate]]. The council, among other things, decreed the original Nicene Creed.