Athanasius and Eternal Sonship
For Athanasius, the eternal Father-Son relationship implies and suggests an eternal generative act, the eternal begetting of the Son, an act of divine self-differentiation that results in the Son's sharing the same divine nature or being as the Father.
Kevin Giles, The Eternal Generation of the Son: Maintaining Orthodoxy in Trinitarian Theology (Downers Grove, IL: InterVarsity Press, 2012), 9