Barth famously remarked—I paraphrase—that Schleiermacher's theology could only be rejected by one who had first loved it. Only within an awareness of its profundity and importance could Barth signal a decisive break with Schleiermacher. The greatest tribute a contemporary Thomist can pay to Bruce McCormack is to echo Barth's sentiments: a Catholic theologian ought to dissent from McCormack's proposal, but his kenotic Christology, together with its correlated theological ontology, is undoubtedly a work of theological brilliance, addressing a crucial Christological question.

Chalcedon seems to leave open the question of how Christ's humanity relates to his divine hypostasis. In McCormack's view, this bequeaths to Christology a basic logical aporia, an unresolved and (more controversially) unresolvable contradiction. The heart of the alleged aporia concerns the impersonalitas of Christ's humanity. In being assumed, Jesus's human nature is added to the logos, but plays no role in constituting the identity of the assuming hypostasis itself. McCormack proposes to ‘repair’ this perceived imbalance by positing a kenosis of the eternal Word, through which the Son's immanent identity is determined as ‘ontological receptivity’ (importantly not passivity) to the human nature of Christ. Consequently, kenosis is construed as an act that begins in the eternity of the Godhead but terminates in time (with and in the person of Jesus). The eternal Son has an essential relation to Christ's humanity; reciprocally, Christ's humanity plays a constitutive role in the life of the eternal Son.

If this argument were taken to be a direct intervention into trinitarian ontology, McCormack's book would be seriously misunderstood. Theology proper follows, in good Barthian fashion, from Christology. The argument is unreservedly Christological; a projected second volume seeks to reconstruct (in a quasi-transcendental manner) what must be true of God's triune life if the Christology developed here is affirmed. McCormack holds that Chalcedon's anhypostaton—the identification the ‘person of the union’ with the divine Word simpliciter—deprives Jesus of any ‘real relation to the person of the union’ (p.61) consequently depriving Christ of ‘any spontaneous self-activating agency’ (p.31) and eliminating ‘agential freedom and responsibility’ (p.11). The Cyrilline tendency to construe one nature as passive and the other as active constitutes an ‘instrumentalisation’ of Christ's human nature in which divine agency seems to impact upon (and work through) a basically passive humanity (‘played’ like Athenagoras's flute). The reintegration of a fully human agency into the basically Chalcedonian pattern can only be achieved through a reconstrual of divine immutabilty in contradistinction to divine impassibility: whereas impassibility asserts the eternally undiminished and unenhanced whatness of divine perfection, immutability asserts the eternally enduring self-identity of God as the God who is for us in Christ (Beständigkeit or ‘constancy’).

Situated relative to nineteenth century kenoticism and to the German-Lutheran interpretations of Barth mediated to anglophone theology by Robert Jenson, McCormack's ‘ontological receptivity’ thesis avoids the pitfalls of post-Barthians such as Jüngel (and Jenson) who tend to collapse the logos into the historical life of Jesus of Nazareth. Likewise, it avoids the Erlangen school's positing of a speculative logos asarkos as the subject of kenosis (as temporary depotentiation of the logos through a divestment of particular perfections). McCormack is not satisfied with a Balthasarian reading that posits kenosis as the temporal actualisation of something paradigmatically actual in the eternal generation of Son. Nonetheless, ‘ontological receptivity’ does not straightforwardly reverse this, as if kenosis indicated the concretization in eternity of that which is temporally actualised in Christ. Such a move would only repeat the retroactive futurist ontology of Jenson, inscribing a misplaced before-after logic that has plagued McCormack in the election-ontology debates.

From Barth, McCormack takes an account of humility-obedience as personal properties of the eternal Son (rejecting an account of ‘kenosis by addition’ by allowing the missions to read back into the processions). Balthasar's account of an ‘active passivity’ in the Urkenosis of the eternal Son-Father relation (doing away with kenosis by depotentiation) is conjoined with Bulgakov's account of God as Absolute-Relative (never lacking a relation to creation) so that the eternal logos is always already co-human as hupostasis (allowing for Christ's humanity to be self-subsistent). The work of Piet Schoonenberg is read alongside McCormack's (evidently crucial) collaboration with Alexandra Pârvan in the construction of a ‘psychological ontology’. Yet it is in the detailed interpretation of scripture that McCormack grounds his proposal. Drawing extensively on Simon Gathercole and Richard Bauckham, some of McCormack's assertions remain questionable: is the controlling significance of the Johannine prologue not indicated by the canonical texts themselves, rather than just the interpretative lens of fifth century Christology? Is the decision to use the second half of Philippians 2:6-11 to illuminate the first not questionable?

McCormack's extensive and masterful historical chapters tackle patristic, eighteenth- and twentieth-century thinkers, but engagement with scholastics is limited, largely to Turretin and Owen. Some engagement with medieval thought could have clarified key distinctions, including how McCormack divides the ontological labour between ‘person’ and ‘nature’. McCormack appropriates Dunn's rebuke of Gathercole (‘naivete concerning the category of person’) against Barnes, but does McCormack himself avoid this critique? Few medievals would be as quick to concede that a fully agential account of Christ requires the abandonment of the anhypostaton. In places, McCormack seems to elide debates concerning the impersonalitas of Christ's humanity and Christ's esse secondarium (indeed, McCormack is keen to overcome post-Barthian aversion to protology, but what role does created nature play in his Christology?). The appeal to the invisible mission of the Spirit to Christ's humanity as potentially carrying some of the ontological burdens of the hypostatic union veers towards a confusion of the grace of union with Christ's (accidental) habitual grace. Likewise, issues of causal ontology recur frequently: McCormack's account of ‘instrumentalisation’ is an excellent presentation of what Thomists understand themselves to be excluding by affirming Christ's humanity to be the conjoined instrument (organon) of his divinity. It is, on at least some readings of ‘instrumentality’, precisely the instrumentality of Christ's humanity that allows his human acts to be construed as acts of the Word (albeit not acts that constitute the Word), thereby elevating and ennobling the sense in which Christ is a subject. More instrumentality rather than less might serve a similar purpose to McCormack's kenosis! Indeed, greater attentiveness to these issues (and, say, the work of Richard Cross) might enable a more sympathetic reception of Rowan Williams's Christ the Heart of Creation than is offered here.

McCormack's account of kenosis is avowedly Reformed: it avoids the interpenetration of natures (and associated discussion of the genus maiestaticum and genus tapeinoticum) that characterises Lutheran Christology after Cheminitz (though other Reformed theologians might contend that the extra Calvinisticum ought to play an equally central role in any authentically Reformed Christology). An assessment of McCormack's contribution will largely depend upon the extent to which his diagnosis of Chalcedon's lacunae—and his assessment that an unresolved question is unresolvable—is accepted. Those addressing similar issues might (emerging neo-Chalcedonianism, e.g.) find resources in Maximus to excavate an alternative (and less revisionary) repair (or repristination) of Chalcedon through a thicker ontology of personhood.

McCormack is sanguine about the reception of his proposal by Catholics. Certainly, formal objections will oppose his distinctively Protestant willingness to revise dogmatic definitions; material objections cluster around his reconstrual of divine simplicity. Nonetheless, if Balthasar's trinitarianism can be assimilated into the Catholic Denkform, why not McCormack's kenoticism? (The latter, of course, will prove more resistant to the metaphysical prophylaxis necessary to assimilate the former). Those who balk at such an undertaking will have more to worry about in the remaining volumes of McCormack's trilogy, but to think (provocatively) with McCormack beyond McCormack, is kenoticism as ontological receptivity not, prima facie, more Chalcedon-consistent than Balthasar's abjected Christ of the Descensus?

I was a neophyte theologian in St Andrews when McCormack presented the Urtext of this book there. Much has evolved in McCormack's thought since then. At the time, there seemed to be only two theological shows in town: Barth and/or Aquinas. My unformed intuition was that the extent to which these were basically opposed (‘or’) or two complementary orientations (‘and’) depended upon the extent to which Barth's category of Entsprechung (‘correspondence’) could be read in terms of analogy. If McCormack's dialectical reading of Entsprechung as ‘ontological receptivity’ is the only Barth-consistent reading (a claim he does not make directly), it signals an insuperable divide. So perhaps McCormack's trilogy will unwittingly convince me that there is only one trajectory still viable. Either way, McCormack's first volume is as exciting as it is brilliant; his trilogy will demand sustained ecumenical engagement.