Tanner's reflections on human nature center on the question: What does it mean that humans are created in the image of God?
One common answer, which Tanner begins with, is that humans possess some trait or capacity that is analogous to God's nature. For example, some have suggested that humans reflect the image of God in that we possess intellect and rationality. As Tanner writes:
Different creatures can be more or less the image of God in virtue of their particular created characteristics. Human beings in virtue of their rationality, for example, might naturally be better images of God's own Word and Wisdom than creatures without intelligence.
And yet, while Tanner accepts this sort of "imaging," she ultimately rejects creaturely imitation as the deepest meaning of what it means for us to carry the image of God. Tanner calls creaturely imitation--the notion that our creaturely traits or characteristics reflect God's image--"weak imaging." The reason for this is because of the radical ontological difference between creatures and God. That is, any creaturely characteristic, like intelligence, is so ontologically diminished when compared to God, such a poor, broken reflection, that it can scarcely be called "the image of God." Further, creaturely imaging suggests that creaturely perfections, endowments or behaviors, can create a ramp upward toward God's perfection through human striving.
In contrast to this "weak imaging" Tanner suggests that there is "strong imaging," where humans reflect the image of God by directly receiving and participating in God's own self and life. And this life isn't produced through creaturely striving, it comes to us as a gift. As Tanner writes,
God finds a way, however, to communicate the goodness of God's own life to creatures without abolishing of mitigating the difference between them and God. In a second, much stronger way of being an image through participation in what one is not, creatures would receive the divine image itself for their own, and end the futile struggles, so to speak, to approximate God in and through what they are simply in themselves. Creatures would receive from God what is beyond themselves--the divine image itself--and be considered the image of God primarily for that reason. They would image God, not by imitating him, but in virtue of the gift to them of what remains alien to them, the very perfection of the divine image that they are not, now having become their own. Rather than being in themselves merely similar to what God is in some full and perfect fashion beyond their reach, they would share in, hold in common with God, what is and remains itself divine, the perfect divine image itself.
Tanner calls this sort of "strong imaging" the imaging of "participation," and, per the title of her book, Christ is our key to understanding here. Christ reflects the image of God not through some human trait or characteristic pushed to the heights. Christ isn't supersmart or superstrong. Christ is, rather, the image of God through participation. "I and the Father are one," Jesus says. Jesus says the Father lives in him and works through him. And in this humanly participation in the life of God Christ shows us how human nature can strongly reflect the image of God.
