Aquinas and Ad Intra Procession

[for Aquinas]...the "procession" of the Son and the Spirit, each in their own way, takes place in eternity within (ad intra) the life of God.

 

Kevin Giles, The Eternal Generation of the Son: Maintaining Orthodoxy in Trinitarian Theology (Downers Grove, IL: InterVarsity Press, 2012), 5