During Athanasius’ life a particular stance on the person of Jesus was being promulgated, Arianism. Arianism is basically derived from the following argument: if Jesus was begotten by the Father, then there must have been a time when he did not exist, hence he is not very God, but instead a created being. Arianism seems very logical on its own terms, and it is even a popular stance taken by some religions during our day.
Although it seemed logical and popular, Athanasius saw that Arianism was profoundly unbiblical. He perceived that this issue demanded attention, as its attack is not on doctrinal periphery, but rather the very heart of the Christian gospel. If Christ is not God, then he is inadequate to take the sins of the world upon himself. If Jesus was created, then he is not eternal, and if he was made to become like god for the purpose of redemption, then God the Father is essentially deficient from the outset. This realization caused Athanasius to stand firmly on the conviction that Jesus Christ is just as much eternally God as the father is, even when the idea was certainly not decided in his day. Listen to his words:
But such heretics no Christian would bear; it belongs to Greeks, to introduce an originated Triad, and to level It with things originate; for these do admit of deficiencies and additions; but the faith of Christians acknowledges the blessed Triad as unalterable and perfect and ever what It was, neither adding to It what is more, nor imputing to It any loss (for both ideas are irreligious), and therefore it dissociates It from all things generated, and it guards as indivisible and worships the unity of the Godhead Itself; and shuns the Arian blasphemies, and confesses and acknowledges that the Son was ever; for He is eternal, as is the Father, of whom He is the Eternal Word.1
So everyone who acknowledges me before men, I also will acknowledge before my Father who is in heaven, but whoever denies me before men, I also will deny before my Father who is in heaven. - Mt 10:32–33
1 Athanasius of Alexandria, “Four Discourses Against the Arians,” in St. Athanasius: Select Works and Letters, ed. Philip Schaff and Henry Wace, trans. John Henry Newman and Archibald T. Robertson, vol. 4, A Select Library of the Nicene and Post-Nicene Fathers of the Christian Church, Second Series (New York: Christian Literature Company, 1892), 317.
2 Mark Galli and Ted Olsen, “Introduction,” 131 Christians Everyone Should Know (Nashville, TN: Broadman & Holman Publishers, 2000), 17.