John Webster on how the doctrine of Trinity saves us from a merely negative, functional definition of divine aseity:

“Aseity is not to be defined merely in negative terms, as the mere absence of origination or dependence upon an external cause. If this is allowed to happen, then a subordinate characteristic of aseity (God’s ‘not being from another’) comes to eclipse its primary meaning (God’s ‘being in and from himself’)…. Aseity is not merely the quality of being (in contrast to contingent reality) underived: it is the eternal lively plenitude of the Father who begets, the Son who is begotten, and the Spirit who proceeds from both…. In this perfect circle of paternity, filiation, and spiration, God is who he is.”

“Life in and of Himself,” in Engaging the Doctrine of God: Contemporary Evangelical Perspectives, ed. Bruce McCormack (Baker Academic, 2008), 114-115.