Saint Athanasius was a prominent Christian theologian and bishop of Alexandria in the 4th century. He is best known for his strong defense of the doctrine of the Trinity and his opposition to Arianism, a belief that denied the divinity of Jesus Christ. Athanasius played a crucial role in the formulation of the Nicene Creed during the First Council of Nicaea in 325 AD. Athanasius was exiled multiple times due to his beliefs and conflicts with various emperors. He is recognized as a Doctor of the Church and is celebrated for his writings, including "On the Incarnation," which explores the nature of Christ and salvation. His feast day is observed on May 2 in the Western Church and January 18 in the Eastern Church.