In his book on the Trinity, Veli-Matti Karkkainen gives a superb detailed summary of Moltmann, and offers some pointed, even devastating, criticisms.
Moltmann puts the cross as the center of his understanding of God: “the cross of the Son stands from eternity in the centre of the Trinity.” Another guiding assumption is “future as the essence of [God’s] being,” a concept Moltmann borrowed from the Marxist philosophy Ernst Bloch, whose philosophy of hope influenced Moltmann’s work on eschatology. God identifies Himself over against all other gods at the cross; at the cross, He shows Himself to be the God who is revealed in His opposite, in godforsakenness.
And it is not the Son only whose co-suffering with the world is evident on the cross, but the Father as well: “The grief of the Father is here as important as the death of the Son.” He insists that “what happened on the cross was an event between God and God. It was a deep division in God himself, in so far as God abandoned God and contradicted himself, and at the same time a unity in God, in so far as God was at one with God and corresponded to himself.” Moltmann also describes this as a loss and restoration of personal identity for the Persons. The Son loses sonship by subjecting Himself to abandonment, and the Father loses His fatherhood in losing the Son. But in the midst of that contradiction, they are united in love for the creation, a love that proceeds as the Spirit.
Moltmann teaches that the persons of the Trinity are dependent on one another, and that they are mutually constituted by one another. He denies that Person can be reduced to relation, insisting instead that there “are no persons without relations, but there are no relations without persons.” The Persons of the Trinity “ex-ist totally in the other: the Father ex-ists by virtue of his love, as himself entirely in the Son; the Son, by virtue of his self-surrender, ex-ists as himself totally in the Father.” Only in this way can Trinitarian theology outwit the static categories of classical theism, too much Hellenized: “Then only does the eternal life of the triune God become conceivable; its eternal vitality becomes conceivable too.”
God must be co-sufferer because He is love: “he suffers from the love which is the superabundance and overflowing of his being,” and “A God who cannot suffer is poorer than any man. For a God who is incapable of suffering is a being who cannot be involved. Suffering an injustice do not affect him . . . But the one who cannot suffer cannot love either. So he is also a loveless being.” Moltmann addresses the problem of God’s freedom in terms of love: “God’s freedom can never contradict the truth which he himself is,” and that truth is love. As Karkkainen puts it, “Love can never exist alone; love shares; love gives.” The traditional idea of divine freedom is, Moltmann argues, based on the notion of domination and lordship, rather than the fundamental Christian revelation that God is love. God’s freedom consists in the friendship that he offers creatures, and in this sense Moltmann says “God ‘needs’ the world and man. If God is love, then he neither will nor can be without the one who is his beloved.”
More fully: “Creation is the fruit of God’s longing for his Other and for that Other’s free response to the divine love. That is why the idea of the world is inherent in the nature of God himself from eternity . . . . And if God’s eternal being is love, then the divine love is also more blessed in giving than in receiving. God cannot find bliss in eternal self-love is selflessness is part of love’s very nature. God is in all eternity self-communicating love.” For Moltmann, creation is an act of self-humiliation and self-limitation. God clears out to create space for the world to be: To make something “‘outside’ himself, the infinite God must have made room for this finitude before hand, ‘in himself.’” There is a sense in which creation itself is the zone of godforsakenness.
The unity of the Triune Persons is a perichoretic unity: “we have understood the unity of the divine Trinitarian history as the open, unifying at-oneness of the three divine Persons in their relationships to one another. If this uniting at-oneness of the triune God is the quintessence of salvation, then its ‘transcendent primordial ground’ cannot be seen to lie in the one, single, homogenous divine essence (substantia) or in the one, single, absolute structure. It then lies in the eternal perichoresis of the Father, the Son and the Spirit.” This perichoretic union is not secondary to the life of God, as if God were once three independent individuals who later unify; because it is eternal, it is the unity of God: “The unity of the triunity lies in the eternal perichoresis of the Trinitarian persons. Interpreted perichoretically, the Trinitarian persons form their own unity by themselves in the circulation of the divine life.” As a perichoretically united society of persons, the Trinity is open to creation, open to inhabit and be inhabited. The goal of creation is the indwelling of God in creation, and this destination is anticipated and participated in by the church in worship. In doxology, the immanent Trinity that comes to the fore.
Karkkainen summarizes the criticisms of Moltmann in some detail. He has been charged with tritheism, and even his most sympathetic interpreters have trouble seeing how he can account for the unity of God. Similar objections have been raised against Moltmann’s apparent rejection of the immanent Trinity: “Moltmann argues that the economic Trinity not only reveals the immanent Trinity but that it also has a retroactive effect on the immanent Trinity.” In Moltmann’s own words, “the pain of the cross determines the inner life of the Triune God from eternity to eternity.” Pannenberg objects to this construction: “This steals from the Trinity of salvation history all sense and significance. For this Trinity has sense and significance only if God is the same in salvation history as he is from eternity.” Moltmann has also been unclear about what he means by talking about the death of God. Karkkainen again prefers Pannenberg: “the Son of God, though he suffered and died himself, did so according to his human nature.” Others have criticized Moltmann for robbing God of any real ability to overcome the evil and suffering that He enters into out of love for us. Moltmann is so fearful of domination and any theology of lordship that he presents a God who can only endure with us, but cannot really deliver.
Karkkainen also notes that some, intriguingly, have charged Moltmann with modalism.: “I wonder with some others whether the charge of modalism lurks behind his program in the form of patripassianism. When the Son suffered and died on the cross, the Father did so with him. Moldmann is aware of patripassionist leadings, and, against Christian tradition, does not necessarily consider it heretical.”