The impression that the theologians of the fourth century such as Athanasius and the Cappadocian fathers were attempting to rationalize away the mysteries of God is... completely mistaken. In fact, they were trying to protect the mystery of the gospel and the God of the gospel from false rationalization. The uses of extrabiblical and somewhat philosophical language such as homoousios in no way detracts from this. For them, homoousios and terms like it are expressions of mystery, not rationalizations that take away from the mystery of the Godhead. It was the Arians and Sabellians and other heretics who were attempting to make Christian belief too simple and too intelligible to human intellect by rejecting the mystery of God as one substance (being) and three distinct subsistences (persons). Exactly how that could be is not fully intelligible to human minds, and heresies reduced the mystery to something mundane and comprehensible and in the process robbed it of its majesty and glory. The orthodox defenders of the doctrine of the Trinity knew that they were standing before mystery when they examined the three-in-one God and the equality of Jesus Christ with the Father. If they sometimes used seemingly complicated and difficult-to-understand formulas and terminology, it was only to defend a mystery.
From Roger E. Olson, The Story of Christian Theology: Twenty Centuries of Tradition and Reform (Downers Grove: InterVarsity Press, 1999), 174.