There is a popular rumor about the Church Fathers, such as Athanasius, having imported foreign categories into theology proper. It charges that Christianity's understanding of Jesus Christ since the fourth century is deeply infiltrated by paganistic Greek philosophy.
The famous case is none other than the word homoousios' (Greek: 'of the same substance'), which is seen as a dubious theological imposition on the earliest Christians' historical experience of God and Jesus, to which has since distorted the (trinitarian) idea of divinity in the consciousness of the Church. To inquire into this matter, we may look back into the uncompromising dispute between Arius and Athanasius.
The Alexandrian presbyter Arius and his followers (Arians) challenged one of the most sacred conviction among the Christians in the fourth century. They proposed that Christ is not God but simply a pristine being created by God. Hence the Son does not exist eternally.
The main person who was more than able to engage the Arians was Athanasius, Bishop of Alexandria at that time. He insisted that the Son exists eternally along God and shares the same divine nature. Although Athanasius is not the one who introduces the term homoousios to the world, he is the best known defender of it in that century.
Hence if homoousios is an invalid theological construct, we would have Athanasius to blame. But we have to ask whether is this the case?
Those of the view that the Bishop is responsible to corrupting Christianity's theology proper often do not realize what was at stake in the Arian controversy. Alasdair Heron has helpfully elaborated that the main contention in the dispute is due to the different paradigm held by Arius and Athanasius. To quote Heron extensively,
(Alasdair I. C. Heron, 'Homoousios with the Father,' in The Incarnation: Ecumenical Studies in the Nicene-Constantinopolitan Creed A. D. 381, ed. Thomas F. Torrance [UK: Handsel Press, 1981], pp.70-71. H/T: Leow Theng Huat.)
The origins of the Arian conception of God lay in the tradition of philosophical theology which had begun with Xenophanes. This took as axiomatic an absolute distinction between God and the world, which was closely bound up with equally radical disjunctions between the mind and the body, and between the intelligible and the sensible realms. Thus the being of God, while in one sense seen as totally separate from non-divine being, is yet implicitly conceived of as being epistemologically accessible to the mind whose vision is clarified and refined. Through self-knowledge lies the path to knowledge of God, and the being of God may be grasped and spoken in terms drawn from the mind's self-analysis, and then further qualified to take account of the difference even between the mind and God. [...] Athanasius does not entirely reject this sort of approach: it has a part to play in his theology, as in most Christian theology before and since. What he does insist on, however, is that this avenue to knowledge of God must be controlled by the fact that God himself has made himself known in Christ, and that it is with Christ as God that genuine knowledge of God must begin. Arius on the other hand never reaches the point where he can admit that Christ is God: his thought is wholly shaped by these other influences, and his epistemological starting-point is thus at the opposite pole from Athanasius.
The Arians' paradigm is traced back to Xenophanes, while Athanasius' back to "the fact that God himself has made himself known in Christ". To understand Athanasius's point further, we may juxtapose it with the historical findings of Larry Hurtado,
To judge by NT writings, Jesus was not reverenced at the expense of God, but instead as the unique agent and expression of God (e.g., as God’s “Image,” “Son”), and in obedience to the one God, who has designated Jesus as the “Kyrios” to whom this robust cultic reverence is to be given.
In the historical context, it is a novel development: professing the “one God” of Israel and yet also including as rightful (even required) recipient of devotion a distinguishable, second figure. The NT evidences, not dreams of some future time when a messianic figure may be reverenced (as, e.g., in the “Similtudes” of 1 Enoch), but instead a real and dramatic re-formulation of regular devotional practice in historically identifiable circles of early Christians. Given the special significance attached to worship practice, the programmatic inclusion of Jesus as co-recipient/recipient of their devotion is remarkable.
Of course, these first Christians insisted that they remained true to the “monotheistic” stance inherited from the ancient Jewish tradition. But, judging by the actual way that they practiced their worship and larger devotional life, theirs was a distinguishable form of “monotheistic” practice involving the programmatic inclusion of Jesus along with God. (Emphasis added)
With this juxtaposition, we see that the theological term homoousios is not a distortion, but rather the approximated term that is considered to be the most appropriate constructed description of the earliest Christians' knowledge of God and Jesus.
It seems clear that Athanasius is well aware that homoousios is not a foreign imposition forced into the theology proper of the Church. In contrast to the Arians, who were too ready to perceive God and Jesus through Xenophanes' philosophy, Athanasius understood well the 'novelty' of the earliest Christians' encounter with God and Jesus. The employment of homoousious is therefore used as a restrictive category that prevents the perception of God from being corrupted by foreign ideology. And precisely because of its preventive function, the category enables Athanasius to describe the relationship between the Father and the Son as how it was encountered by the earliest believers. To him, the theological notion that Jesus shares the same divine nature as God is not something he pulled out from the air but a responsible exercise of historico-theological construction. Instead of being the epitome of the invasion of Greek philosophy on theology, homoousios is the necessary category to avoid precisely that during the fourth century.