The Athanasian Creed (Quicumque Vult) is a statement of Christian Trinitarian doctrine and Christology which has been used in Western Christianity since the sixth century A.D. Its Latin name comes from the opening words Quicumque vult, “Whosoever wishes.” It is the first creed to explicitly state equality of the persons of Trinity.
The first half of the creed confesses the Trinity (one God in three persons). With didactic repetition it ascribes divine majesty and characteristics to the Father, Son, and the Holy Spirit, each individually. At the same time it clearly states that, although all three are individually divine, they are not three gods but one God. Furthermore, although one God, the Father, Son, and Holy Spirit are distinct from each other. For the Father is neither made nor begotten; the Son is not made but is begotten from the Father; the Holy Spirit is neither made nor begotten but proceeds from the Father and the Son.
Didactic as its content appears to contemporary readers, its opening sets out the essential principle that the catholic faith does not consist in the first place in assent to propositions, but ‘that we worship one God in Trinity, and Trinity and Unity’. All else flows from that orientation.
Its teaching about Jesus Christ is more detailed than in the Nicene Creed, and reflects the teaching of the Council of Ephesus (A.D. 431) and the definition of the Council of Chalcedon (A.D. 451). The Athanasian Creed boldly uses the key Nicene term homoousios (‘one substance’, ‘one in Being’) not only with respect to the
relation of the Son to the Father according to his divine nature, but that the Son is homoousios with his mother Mary, according to his human nature.
The Creed’s wording thus excludes not only Sabellianism (the nontrinitarian belief that the Heavenly Father, Resurrected Son and the Holy Spirit are different modes or aspects of one God, as perceived by the believer, rather than three distinct persons in God himself) and Arianism (the heresy that taught that Jesus was not one with the Father, and that he was not fully divine in nature), but also the Christological heresies of Nestorianism (the heresy that taught that Christ exists as two persons, the man Jesus and the divine Son of God, or Logos, rather than as two natures [True God and True Man] of one divine person) and Eutychianism (the heresy that taught that the human nature of Christ was overcome by the divine, or that Christ had a human nature but it was unlike the rest of humanity). A need for a clear confession against Arianism arose in western Europe when the Ostrogoths and Visigoths, who had Arian beliefs, invaded at the beginning of the fifth century (excerpt taken from Wikipedia). Today, Trinity Sunday, we will say the Anthansian Creed in place of the Nicene Creed.