How is God involved in our lives? We often have difficulty answering this question. And when we do answer it, our ideas tend to be simplistic. We either think of God as an alien, almost magical force that immediately and directly intervenes in our lives, or we think of God as an enhancement—a better and larger version—of our natural capacities. Throughout her writing, theologian Kathryn Tanner, who recently joined the Yale Divinity School faculty, has provided us with more nuanced understandings of God’s activity.

In Christ the Key, she presents a theological vision based on the premise that God gives the fullness of God’s own life to us through Christ. Although she draws on Neoplatonic strands of early Christian theology, her approach is eclectic (for example, Karl Barth is also an important, if implicit, influence). Her intent is to exercise a “creative deployment” of the history of Christian thought in order to help us better understand how Christ is key to what God is doing everywhere. She then uses this vision to open new ways of approaching “otherwise tired theological topics.”

Her first topic is human nature. We usually think that we are created in God’s image (following Genesis) because we—unlike other creatures and like God—have reason and free will. By contrast, Tanner argues that what characterizes humans is that we are very much unlike God. We lack definition. Having an “exaggerated plasticity,” we are malleable to outside influences and open to radical transformation.

We participate in God’s image only by participating in what we are not—God. We participate in God in a “weak sense,” along with other creatures since God is the source of all life, and we need Christ in order to participate in God’s image in a “strong sense.” In Christ, the humanity of Jesus is perfectly united with the word and wisdom of God. Christ, therefore, is the model and the means—through the power of the Spirit—for our being molded by the very impression of God’s image in a human life formed according to its pattern.

This has implications for how we understand grace. Here Tanner seeks to bridge the usual divides between Protestant and Catholics—pushing both in new directions. Like Catholics, she argues that nature rather than sin needs to be our reference point for understanding grace. We need grace not because we are stuck in sin but because we are incapable of imaging God on our own. She combines this hallmark of Catholicism—grace perfects nature—with Protestant pessimism. Existing without grace in a state of sin is a dire predicament because we lack what we need in order to mirror God’s image within us. Because of the radically discontinuous distance between God and humans, we need the Word and the Spirit externally imparted to us. We are transformed not by adding to what is already inherent to our nature, but by being given the free gift of God’s grace.

Christ is also key for understanding the Trinity and its significance for us. Because Jesus is the Word of God, his relationships to the other members of the Trinity give us a picture of trinitarian life. In an incisive portrayal of biblical accounts of these relations, Tanner perceptively navigates Eastern and Western Christian divides on the question of whether the Spirit proceeds from the Father or from the Father and the Son. Here she does justice to both the East’s emphasis on the Spirit and the West’s emphasis on the work of Christ within the Trinity.

Moreover, her chapters on the Trinity include an especially discerning critique of attempts to base modern ideas about human relationships and about how societies ought to function in relation to the Trinity. Instead of drawing direct parallels between the Trinity and human community, Tanner recommends that we focus on participating through Christ in the Trinity’s work in the world. This enables us to avoid both unrealistic politics (since human beings are not the Trinity) and uncritical complacency (since participating in trinitarian life does make a difference in the world).

In addition, a vision of the incarnation enables Tanner to provide a thoughtful response to feminist and womanist concerns about the cross (for example, that the vicarious satisfaction and penal substitution models of atonement present an abusive God). The point of the cross, she contends, is not suffering and death, but rather that in and through it—in the midst of our sinful, conflictual and death-dealing world—God works unswervingly for our good by struggling against the forces of sin and death in the greatest possible solidarity with us.

Finally, Christ is key for understanding the Holy Spirit’s involvement in our lives. As God’s work in Christ does not eradicate Jesus’ humanity or push it aside—in the way that one competing power would take over another—so the Spirit works in and through the often messy and conflict-ridden processes of human life. In the appearance of human frailty and failure on the cross, God’s power is fully present in Christ, reworking, healing and elevating the human beyond itself; so in and through our humanity—as we participate in Christ’s own—we are given a whole new character in the Spirit. Out of sin and death comes what we would never expect or predict: a new way of being. Throughout all that happens to us—even in conflict, suffering and loss—the Spirit re-forms and reworks us as a whole into “a life-giving, Spirit-filled form.”

Christ the Key clearly moves us beyond simplistic ideas about God. It portrays how within the concrete circumstances of human life, God gives the abundance of God’s very own life and not simply a created version of it. Through Christ, God fully enters humanity and thereby attaches us, precisely in our frailty and finitude, to God. This insight has profound practical implications for understanding how God is involved in the world—healing, transforming and reworking all that we experience.

Some may find Tanner’s arguments too technical. Others will quibble with specific points, depending on their theological perspectives. But regardless of one’s standpoint, Tanner’s innovative and eclectic interpretation of Christian thought will surely stimulate further reflection on how God gives us the “goods of God’s own life” and thereby establishes “the closest possible relationship with us as that comes to completion in Christ.”