Christ the Key is the promised sequel to Jesus, Humanity and the Trinity (2001), but even more, it is the culmination of Kathryn Tanner's entire career to this point, a career in which she has carefully unfolded the implications of two remarkably fruitful ideas. The first is that God always remains absolutely transcendent over creation, such that God and creatures can never stand in any kind of competitive relationship. The second is that God is the giver of all good gifts. Above all, God wants to give to human beings the gift of God's own divine life. Christ is himself the fullest form of this gift, ‘the culmination and completion of what is true generally of God's interactions with us’ and so ‘the key to what God is doing everywhere’ (p. viii).
The first three chapters apply this Christology to the classical loci of theological anthropology: what it means that human beings are made in the image of God, that we are fallen, and that we are redeemed through grace. Only the divine Word, the second person of the Trinity, is the true image of the Father, according to Tanner, but the perfect unity of divine and human natures in Christ make him the perfect human image of the second person. Whereas patristic and medieval accounts of the imago dei tend to identify it with reason or free will, Tanner argues that human nature images God by being essentially plastic, expandable and open-ended. ‘In contrast to other creatures, human beings are unusually flexible, capable of adapting, of altering their behaviors in order to adjust to changing social and natural environments’ (p. 41). Reason and free will are simply especially pertinent examples of our general capacity for openness. Yet Tanner is no process theist. Human plasticity images God not because God is the perfect adapter but because God is unlimited and incomprehensible: ‘Humans imitate God's incomprehensibility by having a nature which is also in a sense unlimited, unbounded by clearly delimited nature, in virtue . . . of an expansive openness’ (p. 53). Tanner thereby presents a very contemporary account of human nature alongside a very traditional account of the divine nature. The resulting synthesis illuminates both, and is indicative of her method throughout the book.
Humans can also image God in a much stronger sense, through participation in Christ. Similarly, they can lose the image in this stronger sense, through sin. Tanner's discussion of the plasticity of human nature grounds her discussion of both of these claims. According to Tanner, human beings need spiritual gifts to image God in the stronger sense, not because we have sinned but simply because we are creatures. We have been created such that, even apart from the fall, our natural faculties must be supplemented by supernatural gifts in order for them to function properly: ‘our faculties were made to operate as they should, to operate well, only when incorporating what remains alien to them, the very perfection of Word and Spirit themselves’ (p. 28). This claim follows from the fact that we are not good or wise by nature (we are not anything by nature; we are plastic) and so we can only be good and wise insofar as we are shaped from without by God, through attachment to Christ. Tanner thus stands in the tradition of those who argue that humans were created spiritually unfinished, designed to appropriate the divine image only gradually. Instead of developing as God wished, however, we mistook God's alien spiritual gifts for our own natural endowment, blurred the line between creature and creature, fell into the mire of sin, and lost the spiritual gifts which allow us to be good and wise (pp. 32–5). There are worries here, both historical-critical and philosophical. Who exactly is the ‘we’ that lost ‘our’ gifts? And if humans were so immature as to make such a disastrous mistake almost immediately, then isn't God a rather incompetent creator? These worries are not irresolvable, but I wish Tanner had addressed them.
Interestingly, Tanner deploys the traditionally Catholic correlative categories of nature/grace instead of the traditionally Protestant categories of sin/grace in a way which allows her to reconcile some of the key claims of both traditions. Tanner conceives human nature primarily as a lack – as the absence of supernatural gifts – rather than as something positive to which grace superadds, and so ‘human nature need not be affected at all for total depravity to be our condition’ (p. 67). On the other hand, on Tanner's account, grace (though extrinsic to our nature) is an essential ingredient of our constitution, which threatens to undermine the integrity of human nature and the gratuity of grace. Chapter 3 is devoted to showing that these consequences need not follow. She argues that human beings have a desire for God which is not ‘natural’ but is itself called into being by the gracious presence of God, and that the integrity of human nature is respected because nothing which is essential to human nature has to change for God to be present to us in the highest possible way.
Chapter 4 argues that, because Jesus is the incarnate Word, his human life takes on a trinitarian pattern. Accordingly, we should look to the New Testament depiction of Jesus as a way for understanding what the trinitarian relationships are like and what they mean for us as organising principles for living. When our lives are joined to Christ in grace, they take on a trinitarian shape. By contrast, in chapter 5, Tanner argues convincingly against various overly facile political readings of the Trinity found in contemporary theology. According to Tanner, there are no necessary connections between monotheism and political authoritarianism, nor between trinitarianism and egalitarianism. Furthermore, efforts to model human communities on the trinitarian relations do not take the absolute transcendence of God seriously enough. Rather than trying to build trinitarian communities, we should strive to imitate Christ, who simply is the trinitarian form of human social life (p. 237). Chapter 6 presents Tanner's incarnational account of the atonement and the cross. Tanner insists that ‘incarnation becomes the primary mechanism of atonement’ (p. 252) because it is the incarnation – understood as the entire life and ministry of Christ – which establishes the closest possible union between God and humanity (pp. 252, 257). Tanner thereby joins feminist and womanist theologians who refuse to valorise death and suffering and so reject traditional, cross-centred theories of the atonement.
Though I accept her shift to an incarnational model of the atonement, I confess that I still do not fully understand Tanner's own account of the mechanism whereby Christ saves us. In particular, I do not understand why what happens to Christ's humanity in the incarnation – the fact that it is brought into ever closer communion with the Word – also happens to our humanity now. Patristic and medieval thinkers had an answer to this question: in the incarnation, Christ assumed human nature as such, with the result that Christ's humanity is our humanity. But I take it that Tanner (rightly) does not accept this view (see e.g. p. 258). With what would she replace it, however? Earlier in the book, we are given several formulations like ‘By being in a hypostatic unity with it, by being one with the second person of the trinity, humanity gains a sort of natural connection to the divine comparable to the natural connection which the Word enjoys with the other members of the trinity’ (p. 73). Yet, again, it is Christ's humanity which is in a hypostatic union with the Logos (as in the first part of Tanner's sentence) and so it isn't clear why humanity in general (as in the second part) gains ‘a sort of’ natural connection to the divine.
Tanner also says that we are justified ‘through attachment to Christ . . . through the humanity he shares with us’ (p. 86) and that this attachment is prior to, and a necessary condition of, both sanctification (p. 87) and faith (p. 92). But this formulation only reiterates the problem, since Tanner spells out attachment to Christ in terms of sharing humanity with him. I understand what it means to say that Christ and I share humanity in the sense that we are both human beings, but presumably Tanner's soteriology requires some more robust sense of sharing. As far as I can tell, however, Tanner does not specify what that sense is, which means that she has not really told us why God must take on a human nature in order to give us the gifts which we need. Nor has she told us how we are to receive those gifts.
Tanner is one of most important theologians working today and Christ the Key is her fullest and most interesting theological statement yet. At every point, her arguments are genuinely creative, while remaining thoroughly grounded in the classics of the Christian tradition – indeed, Tanner's footnotes are themselves a short course in the history of Christian thought. Everyone who works in constructive theology could read this book with profit and learn much from it.
