McMartin argues for an understanding of the image of God as the capacity for a (certain sort of) relationship with God. This, however, is not just a relational understanding of the image, but is in fact an ontological and relational and functional model. This is because capacities are structural (i.e. properties of beings, like the capacity to think, to hear, to jump, etc.) but moreover are teleological. Furthermore, McMartin notes that this teleological aspect means that capacities need to be understood in terms of potentiality and actualization. Defining a “nature” as (at least in part) a set of capacities, McMartin therefore is able to conclude that natures have this teleological potentiality/actualization multivalence.

McMartin also notes that capacities have a hierarchical structure, giving the example of the ability to see. A lower level capacity for sight deals with whether one has a functioning set of eyes, whereas a higher level has to do with whether one’s brain can process visual stimuli. A loss of functioning eyes de-actualizes the capacity to see, but the higher level capacity remains intact; if the eyes can be healed, the ability to see will be restored because the higher level capacity remained.

Building on this teleological and hierarchical understanding of natures as a set of ultimate capacities, and in particular the idea of the image of God as the capacity for relationship with God, McMartin offers a Christological discussion of how the two natures and their union in one person could be understood in this light.

First, he says the Son qua Son and thus qua divine is the true image of God (Col 1:15) and “exact imprint of his nature” (Heb 1:3) because he fully actualizes the capacity for relationship with God—indeed, he says that this is why he is called the Son, since it is the result of having the divine nature.

I am a bit leery about this, since it seems to be inadvertently setting up an almost Arian collapse of God with the Father while the Son is a separate being from God who is related to God. Perhaps this could be salvaged with some more carefully Trinitarian language.

Second, he talks about this image bearing capacity in terms of Christ’s humanity. This, I think, is on more solid ground, although he actually does not develop this part very much. He jumps straight ahead to the soteriological implications this has for us in terms of growing in Christlikeness.

I would have suggested here that the passages he cited earlier (Col 1:15, Heb 1:3) should be interpreted under this heading. That he is the image of the invisible God and the exact imprint of his nature does highlight his divine nature, it is true, but the whole point is that he is now the human being that is this. He is the “very image” because he is the culmination and perfect actualization of what human nature was made to be. This, of course, ties in with the supralapsarian view I take regarding the incarnation.

Where things get interesting in this essay is where he turns to consider Christ’s person as capax Dei. Now he leverages the hierarchical and teleological aspects of capacities to suggest several things. First, he suggests a mildly kenotic Christology in which all the divine capacities are fully retained on the level of ultimate capacities (i.e. on the level of what is constitutive of a nature) but inevitably not all are fully actualized in the concrete particularity of the human being, Jesus Christ, since the finitude of a human body cannot fully actualize all divine capacities: “One positive and remarkable capacity comes at the expense of another. Christ’s full, embodied humanity may limit the expression of his divine capacities while not diminishing his full divinity” (147). I’m not convinced that this really is much of an advance; the notion that some divine attributes were retained but not exercised in the incarnation is not new, and is not without problems. Second, and more usefully, McMartin uses his ideas about capacities to turn aside the criticisms of an/enhypostasis. All the capacities of human nature are actualized by him—though of course, the finitude of human nature means that the actualization must be particular (e.g. he must be this height and not every possible height)—so there is nothing Docetic about an/enhypostasis. Third, and most interestingly for me, McMartin comes close to suggesting what I want to propose as a way past dyo- vs. monothelitism. As McMartin puts it, “The model may allow for two ultimate volitional capacities pertaining to each of the natures, but a single will in actualization of the capacities” (148).

McMartin’s last section before concluding is a brief one drawing out some soteriological implications of his ideas. I particularly like what he has to say about the soteriological implications of the relationship between potentiality and actuality:

First, Christ’s example shows that in our pursuit of Christlikeness, we need growth, process, and the movement from potentiality to actuality; even Jesus was not immune from these things (Luke 2:40, 52). This slow and often tortuous movement contrasts starkly with the desire inculcated in us by our culture. We are impatient; we want technological, immediate solutions. We want nonpersonal, nonmessy, less-than-human ways of solving our problems, even with respect to our growth in Christ. We long for supernatural, immediate intervention, in the manner of one of Christ’s healings, rather than long-developed strength of character. (149)