Thankfully, in recent years the doctrine of God has made a comeback among theologians, and deservedly so. The doctrine of God describes who God is and what he does; it encompasses God’s attributes, like omniscience and omnipotence, as well as the mystery of the Trinity. Yet many Christians do not dwell on these truths because they seem dull and disconnected from everyday life. I remember struggling myself, even as a seminarian and intern, when my pastor assigned me to teach a Sunday school lesson where I would show how the Trinity was practical. Yet the Trinity is deeply practical: God being one in three means there is an incomprehensible fullness and sufficiency in God’s inner life. Unlike the gods of cults and false religions, the true God does not need us to supply some absence of relationship or need for glory. He made us and takes care of us because his cup runs over, not because he’s lonely.
God’s fullness in himself is what we call God’s “aseity.” Coming from the Latin a se, “from himself,” aseity describes God as the source of his own life, completely self-sufficient, independent from every cause or need. Acts 17:24–25 serves as a classic proof text: “The God who made the world and everything in it, being Lord of heaven and earth, does not live in temples made by man, nor is he served by human hands, as though he needed anything, since he himself gives to all mankind life and breath and everything.” Likewise, Psalm 50 reveals God’s aseity by reasoning that his people’s sacrifices were always meant to show their reliance on him, not fulfill some need of his: “For every beast of the forest is mine, the cattle on a thousand hills. I know all the birds of the hills, and all that moves in the field is mine. If I were hungry, I would not tell you, for the world and its fullness are mine. Do I eat the flesh of bulls or drink the blood of goats?” (Ps. 50:10–13)
The practical implications of God’s aseity are not as easy to perceive at first as some of God’s other attributes. God’s holiness, for example, clearly shows us our need for his grace, found in the work of Christ. His justice and righteous wrath entail that he will right all wrongs in the world and bring the justice we long to see. God’s faithfulness means he will do what he has promised. He will not change his mind about saving us (Mal. 3:6). We more easily grasp the practical implications of such attributes of God and try to imitate them; we know we should be holy, and just, and righteous, and faithful. But how do we reflect having life in and of ourselves, something that belongs only to God? I want to suggest that we can not only rejoice in God’s aseity but, by God’s grace and the Spirit’s enabling, seek to imitate it in our own limited way as his redeemed image-bearers. Let’s look at two of these ways.
God’s aseity entails his invincibility. Nothing can thwart God’s purposes or overwhelm him. He stands firm against all that is not God. The Christian, united to Christ, faintly but truly echoes this independence, this transcendence of vulnerability and suffering: we are more than conquerors through him who loved us (Rom. 8:37). Even though today we’re like fragile clay jars, with little earthly power or glory, the apostle Paul says we are in a spiritual sense indestructible:
We have this treasure in jars of clay, to show that the surpassing power belongs to God and not to us. We are afflicted in every way, but not crushed; perplexed, but not driven to despair; persecuted, but not forsaken; struck down, but not destroyed; always carrying in the body the death of Jesus, so that the life of Jesus may also be manifested in our bodies. (2 Cor. 4:7–10)
We can be afflicted, but not crushed, because of God’s surpassing power at work in us in Jesus. The independent, impassible God who cannot be destroyed makes us more and more like himself. This is not because of our strength or goodness but because in Christ the indestructible God took on fragile flesh and was crushed in our place—a jar of clay—for our trespasses, yet rose again imperishable (Rom. 4:25).
As we await the invulnerability we will enjoy in heaven, we also imitate God’s aseity in a second way as we freely forgive those who have wronged us. Forgiveness numbers among the most difficult and most beautiful activities in human life. Because we know how easy it is to dwell on wrongs done to us, fueling bitterness and the desire for revenge, we find stories of forgiveness deeply compelling. Cori ten Boom extending her hand to a former Nazi concentration camp officer; Rachel Denhollander pointing her convicted abuser to the gospel; or the young Texan who gained notoriety a few years ago by offering forgiveness to whoever killed her police-officer father. These expressions of forgiveness have a universal appeal and power. And beyond and behind them all, there is Jesus on the cross: “Father, forgive them, for they know not what they do” (Luke 23:34).
As surprising as it may sound, this aspect of the doctrine of God can help us to forgive others and be peacemakers in our relationships. “Be kind to one another, tenderhearted, forgiving one another, as God in Christ forgave you. Therefore be imitators of God, as beloved children” (Eph. 4:32–5:1). God has such a fullness in himself that when he gives he does not lose anything. As creatures, we think in terms of zero-sum exchanges. If you give me your coat, as in Matthew 5:40, you have one less coat. This is the economy of the world we live in, but this thinking can be ruinous for our relationships. Not only does it go wrong in a give-to-get mentality, where we love only those whom we feel do (or will do) a good job of loving us back, but it hinders us from showing grace in all sorts of other ways too. When relationships are frayed, we are often unwilling to overlook offenses or forgive because we think it will somehow take away from us. If I forgive you for what you’ve done, then, people think, I have nothing to leverage against you to get something in return, or to protect my own interests.
The amazing economy of God’s grace does not work like the world’s zero-sum game. Those who trust in God and find true satisfaction in him will echo his aseity. Instead of looking to others for validation, we begin to show grace without needing a pound of flesh in exchange. Forgiveness requires that we bear in ourselves whatever debt someone had towards us (Matt. 18:21–35). Because of the bountiful fullness that God has given us in Christ—every spiritual blessing and an eternal inheritance (Eph. 1, 1 Peter 1)—we can forgive those debts, and in doing so, actually find ourselves less empty and more full. We can do this because our cup already runs over (Ps. 23:5). We experience the double blessing of grace, as Shakespeare’s Merchant of Venice illustrates:
The quality of mercy is not strained;
It droppeth as the gentle rain from heaven
Upon the place beneath. It is twice blest;
It blesseth him that gives and him that takes:
‘Tis mightiest in the mightiest; it becomes
The throned monarch better than his crown:
His sceptre shows the force of temporal power,
The attribute to awe and majesty,
Wherein doth sit the dread and fear of kings;
But mercy is above this sceptred sway;
It is enthroned in the hearts of kings,
It is an attribute to God himself;
And earthly power doth then show likest God’s
When mercy seasons justice.
We will never be the source of our own life like God, for we are his workmanship. Yet he gives us a fullness that enables our generosity. He makes us open-handed givers like himself (James 1:5). As John’s prologue states, “And from his fullness we have all received, grace upon grace” (John 1:16).
Praise God that the One who is full in and of himself shares his fullness and makes us like him.
 See John Webster, God Without Measure: Working Papers in Christian Theology Volume I God and the Works of God (New York: T&T Clark, 2016), 19. Likewise, for works on how the doctrine of the Trinity is practical, see Fred Sanders, The Deep Things of God: How the Trinity Changes Everything (Wheaton: Crossway, 2017) and Michael Reeves, Delighting in the Trinity: An Introduction to the Christian Faith (Downers Grove: IVP, 2012).