The Catholic Church (and other Christian Churches that affirm the Trinity) teaches that Jesus Christ was sent down from Heaven and became man (having tangible flesh and bone, as part of his humanity) to bring forth the union of Christ's humanity and God's divinity in one hypostatic union (aka individual existence). The
duality of Jesus Christ refers to his two natures: divine and human. In Christ, the divine nature and human nature came together in union (a hypostatic union).
The
Athanasian Creed (as I've mentioned before is one of the
Three Core Doctrines of Christianity) is not only a Champion of the Trinity, but also recognizes the
doctrine of the hypostatic union in Jesus Christ. It states that:
"He is God from the essence of the Father, begotten before time; and he is human from the essence of his mother, born in time; completely God, completely human, with a rational soul and human flesh; equal to the Father as regards divinity, less than the Father as regards humanity."What the above basically says is that Jesus Christ is
fully divine in nature due to him being God, which is derived from the essence of God the Father -- God the Father is fully and purely divine in nature. However, he is
ALSO fully human in nature due to him being born from his mother (the Blessed Virgin Mary), who is fully human and was born in time -- she is fully human in nature. She is not a celestial being/deity/etc, but rather she's human in nature like us (except she was born without Original Sin, but that's
a different discussion topic).
Although he is God and human, yet Christ is not two, but one. He is one, however, not by his divinity being turned into flesh, but by God's taking humanity to himself. He is one, certainly not by the blending of his essence, but by the unity of his person. For just as one human is both rational soul and flesh, so too the one Christ is both God and human."This means that Jesus Christ is fully divine AND fully human, not half and half like a demigod from Greek/Roman mythology (e.g. Hercules, Perseus). In the same way the we, as humans, are BOTH soul and flesh, Jesus is BOTH God and Human.
The term
hypostatic union comes from the term
hypostasis (meaning the underlying state or underlying substance and is the fundamental reality that supports all else). It's used to term the description and reasoning of how Christ is fully human and fully divine in nature when he was incarnated. We firmly believe in the Incarnation, which is Church doctrine referring to the conception and birth of a sentient/celestial being who is the material manifestation of an entity/deity, god, or force whose original nature is immaterial (e.g. divine in nature - God the Father is fully and purely divine in nature). The Second Person of the Holy Trinity, God the Son (Jesus Christ), was incarnated and became flesh when he was miraculously conceive by the Blessed Virgin Mary.
The
First Council of Nicaea (325 AD) discussed this topic, due in part because of rising heretical belief in Arianism (from Arius of Alexandria, who argued that Christ was a created being). The First Council of Nicaea, upon denouncing and condemning Arianism, concluded on the word hypostasis (derived from ὑπόστασις (“of one substance”) to signify the absolute equality of God the Son to God the Father.Jesus Christ is neither greater nor lesser in divinity than God the Father, but rather he is equal to God the Father and equal to God the Holy Spirit (as God the Holy Spirit is also equal to God the Father) -- this forms the foundations for
the doctrine of the Trinity.
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As for why we baptize "in the name of the Father, and of the Son, and of the Holy Spirit," this tradition is taken directly from biblical scripture in
Matthew 28:19, which states, "Go, therefore, and make disciples of all nations, baptizing them in the name of the Father, and of the Son, and of the holy Spirit. Some argue that Christ said to the Apostles, especially in the Book of Acts (aka Acts of the Apostles), to baptize in the name of Jesus Christ. HOWEVER, in actuality Christ commanded that the Apostle baptize specifically in the name "Yahshua" (which has been directly translated into Jesus Christ, but the allergorical meaning behind this is lost). This then plays into the belief of the Trinity.
Whenever God revealed himself as a pillar of fire, burning bush, dove, etc., he did not become another God or separate person right? These were
"theophanies," which are God's manifestations visible to humankind. On multiple occasions God revealed himself as the Holy Spirit, sent the Holy Spirit in His name, etc. If the pillar of fire, burning bush, dove, voice of God are not to be considered "separate persons" then why would you consider the Holy Spirit as a separate person? The Holy Spirit, the Third Person of the Trinity, is one theophany as it is one of the manifestations of God that have been revealed to mankind. Jesus Christ, the Second Person of the Trinity, was sent to earth from heaven by God to save mankind -- he is the most perfect theophany (manifestation of God visible to us) and revelation of God because he is both fully human and fully divine (the bridge between God and Man).
Thus, when the disciples baptized using the name of "Yahshua," they used the specific name Yahshua (Jesus Christ) told them to use: the name of the Father, the name of the Son, and the name of the Holy Spirit. Jesus Christ came
in his father's name, the Holy Spirit was
sent in his name; everything done, such as the Sacrament of Baptism, was
centered in God and His (God's) name. he Son’s name, and the Holy Spirit’s name. Belief in the Oneness of God and the Unity of God is necessary to fully accept this, and traditions that came out of church councils and “fathers” are what completely confused this issue, which to me in extremely obvious. When they baptized with the name of Yahshua, they
were baptizing in the God the Father’s name, God the Son’s name, and God the Holy Spirit’s name because the name Yahshua represents God, including the three persons in one God (the Trinity).
The
mystery of the Holy Trinity is
the central mystery of Christian life and faith (according to the Catholic Church and other Christian denominations). The link I've hyperlinked is on the Catechism of the Catholic Church and is a great read for you if you're looking to understand more and have it explained in greater depth the Revelation of God as the Trinity, such as when God the Father was revealed by God the Son (Jesus Christ), as well as when God the Father and God the Son were revealed by the Holy Spirit.