The two documents which inspired this study, according to the first chapter, are the memorandum issued on behalf of the World Council of Churches in 1981 and the Vatican's clarification on the Filioque in 1995. The former contends that the Filioque (the Latin addition to the Niceno-Constantinopolitan Creed of 381) does not compromise the status of the Father as sole principle of the Trinity, but ‘maintains the revealed and accepted taxis’ of the three persons, filling a lacuna in the creed and acknowledging the centrality of Christ to the faith. The latter adds that the Latin tradition upholds the equal divinity of the Son and the Father without (as eastern criticism alleges, according to Lee) subordinating the Spirit to the other two persons, and distinguished between the processing of the Spirit from the Father also and the joint communication of the consubstantial divinity from the Father and the Son. In the light of subsequent exchanges between Congar, Larchet and Zizioulas, Lee concludes that the eastern Church continues to suspect the West of deriving the Spirit not from the Father alone but from the essence of the Godhead, of confusing the divine essence with the divine energies in its account of the imparting of the consubstantial divinity, and of confounding theologia with oikonomia by deducing the ontological dependence of the Spirit on the Son within the Trinity from the mission of the Spirit in this world (p. 69). It is these objections that Lee undertakes to test in the remainder of the book by a comparison between Gregory of Nyssa, the favoured spokesman of the East in western circles, and Augustine, the undisputed fountainhead of western thought on the Trinity, as on so much else.

The chapter on Gregory of Nyssa begins with a useful summary of the presuppositions governing his defence of the Nicene faith against Eunomius. The first is that we know God not (as Eunomius is alleged to hold) in his essence but only by the epinoiai or conceptions that he vouchsafes to us; the second is that there is no transition in God from potentiality to actuality (energeia), and hence no diastêma or interval, either in time or in space, between the Father and the other two persons who have their origin in him. The third is that the nature of God is at once coextensive with the three persons and fully instantiated in each of them; the fourth is that the taxis or order in which they are named betokens no diastema in rank or power. It follows that the Spirit is truly God, and Lee also demonstrates, against Jaeger, that Gregory does not shrink from making the Father the cause of the Spirit, as of the Son. How then are the two differentiated? As Lee perceives, the cardinal text is Ad Ablabium, where the Son is said to mediate, as the one directly caused, between the Father as cause and the Spirit as that which derives from the cause. Rather than deduce that the Son is the cause of the Spirit's existence, Lee distinguishes between a negative and a positive mediation. Inasmuch as the Son is the one who transmits the bounty of the Father to his creatures, he is that which the Spirit is not; on the other hand, inasmuch as the Spirit is ‘of’ the Son, his peculiar role is to be the one who makes the Son known. The abstruseness of the thesis may be a point in its favour rather than against it, though one might wish to see it buttressed by a wider array of texts.

In the chapter on Augustine, it is not so much the paucity as the absence of relevant passages from the De Trinitate that leaves one hesitating to accept Lee's provocative argument that the Son is in a sense a second principium of the Spirit. Knowing that this is a customary charge against Augustine in the Greek tradition, Lee offers as a palliative his translation of De Trinitate 15.29 where the Father is said to be principaliter the source of the Spirit, but to have granted to the Son that the Spirit should proceed also from him, and should thus be communis or common to both (p. 233). From this Lee infers that the Son is said indeed a principium, but only communiter rather than principaliter, and he goes on to quote the phrase commune principium as though it occurred in Augustine. In fact it is found neither at De Trinitate 15.29 nor at 15.47, which Lee quotes on pp. 231 and 234; the Son is indeed a principium at 5.13.14, but of creation, not the Spirit. There is, on the other hand, an appearance of symmetry, if not of co-operation, in Augustine's notorious teaching that the Spirit is the caritas or love between the Father and the Son. As Lee observes (p. 241), this seems to entail the subordination either of the Spirit to the Father and the Son, if love is understood as a function, or else of the Father and Son to the Spirit, if love is the very essence of the Godhead. Lee's attempt to escape the dilemma is as obscure to me as the solutions that he quotes with disapproval from other scholars (pp. 242–2), and I see little reason to labour in defence of a position that Augustine himself so quickly left behind. It seems to me that the chapters on both Gregory and Augustine bear most fruit when they turn from theologia to oikonomia, demonstrating that it is one and the same Holy Spirit, whatever his origin, to whom Augustine ascribes the loving union of the Church with its Head and Gregory the progressive glorification of those whom Christ has joined to his Godhead through the flesh.