Divine Self-Differentiation and Eternity
Divine self-differentiation takes place within the life of God in eternity; what takes place in history simply reveals what is true in eternity....God is triune for all eternity; events in the world neither make him triune nor explain how he is eternally triune. God is certainly revealed in the economy as Father, Son and Spirit, three distinct persons, but it is the Bible that tells us these three persons coexist for all eternity and that these three divine persons are in fact one God. Thus what the doctrines of the eternal generation of the Son and procession of the Spirit do, and do well, is explain how the one God is eternally three persons and how the divine three persons are the one God.
Kevin Giles, The Eternal Generation of the Son: Maintaining Orthodoxy in Trinitarian Theology (Downers Grove, IL: InterVarsity Press, 2012), 5