I thought it would be instructive to review some of Michael Allen Gillespie’s description of Nominalism, and then compare and constructively contrast that with Barth’s actualism. When you read Gillespie’s treatment of nominalism—at least the part I’m going to share—some of it will sound strikingly similar to Barth’s own anti-natural theological impulses; with an emphasis on Divine Revelation to boot. Gillespie writes:
Most nominalists were convinced that human beings could know little about God and his intentions beyond what he reveals to them in Scripture. Natural theology, for example, can proved God’s existence, infinity, and supremacy, according to Ockham, but it cannot even demonstrate that there is only one God. Such a radical rejection of scholastic theology clearly grew out of a deep distrust not merely of Aristotle and his Islamic interpreters but of philosophic reason itself. In this sense, Ockham’s thought strengthened the role of revelation in Christian life.
Ockham also rejected the scholastic understanding of nature. Scholasticism imagined nature to be teleological, a realm in which divine purposes were repeatedly realized. Particular entities became what they already potentially were in attaining their special end. They thus saw motion as directed toward the good. The nominalist rejection of universals was thus a rejection not merely of formal but also of final causes. If there were no universals, there could be no universal ends to be actualized. Nature, thus, does not direct human beings to the good. Or to put the matter more positively, nominalism opens up the possibility of a radically new understanding of human freedom.
The fact that human beings have no defined natural ends does not mean that they have no moral duties. The moral law continues to set limits on human action. However, the nominalists believe that this law is known only by revelation. Moreover, there is no natural or soteriological motive to obey the moral law. God is no man’s debtor and does not respond to man. Therefore, he does not save or damn them because of what they do or don’t do. There is no utilitarian motive to act morally; the only reason for moral action is gratitude. For nominalism, human beings owe their existence solely and simply to God. He has already given them the gift of life, and for this humans should be grateful. To some few he will give a second good, eternal life, but he is neither just nor unjust in his choice since his giving is solely an act of grace. To complain about one’s fate would be irrational because no one deserves existence, let alone eternal existence.
Clearly not a one-for-one correspondence between Ockham and Barth, but there is some similarity between their respective emphases on Divine Revelation as the only point of contact creatures have for a knowledge of God in negation of a natural theological way. One more point of correspondence between the two, respectively, would be the emphasis upon Divine Sovereignty, and God’s relation to the world through covenant rather than through a series of graded conceptions of causality leading to a certain understanding of teleology for the created order.
Yet, Ockham ends up positing a Potentia-God wherein God has two-powers, 1) his absolute, and 2) his ordained. Here there is a rupture placed between the way God may act (according to his absolute) power in his inner and eternal life, versus how he chooses to act (according to his ordained power) in his ad extra or economic life in temporal-salvific reality. For Ockham, because of this strain between the two modes of God there is no guarantee that the God we see in ordained and created reality corresponds to who God actually is in his eternal life; as such we lose any sort of realist connection between what another dualist (Kant) might identify as phenomenological reality vis-à-vis noumenal actuality. Barth doesn’t have this problem.
As George Hunsinger notes in regard to Barth’s actualism and particularism:
“Actualism” is the motif which governs Barth’s complex conception of being and time. Being is always an event and often an act (always an act whenever an agent capable of decision is concerned). The relationship between divine being and human being is one of the most vexed topics in Barth interpretation, and one on which the essay at hand hopes to shed some light. For now let it simply be said, however cryptically, that the possibility for the human creature to act faithfully in relation to the divine creator is thought to rest entirely in the divine act, and therefore continually befalls the human creature as a miracle to be sought ever anew.
“Particularism” is a motif which designates both a noetic procedure and an ontic state of affairs. The noetic procedure is the rule that says, “Let every concept used in dogmatic theology be defined on the basis of a particular event called Jesus Christ.” No generalities derived from elsewhere are to applied without further ado to this particular. Instead one must so proceed from this particular event that all general conceptions are carefully and critically redefined on its basis before being used in theology. The reason for this procedure is found in the accompanying state of affairs. This particular event requires special conceptualization, precisely because it is regarded as unique in kind.
Here we see, per Hunsinger’s treatment of parts of Barth, that there is nothing left ad hoc or potential about the God-world relation. Instead, for Barth Divine reality is known as God makes himself known in the scandalous event of God become man in the elected humanity of Jesus Christ. Herein, for Barth, there is no ‘God behind the back of Jesus’—as there is for Ockham—but instead just the opposite; for Barth God is fully and actually made known without remainder through the Christ event as that becomes actualized over and again, afresh and anew through the miracle of the Evangel. While Barth retains a quasi-Occamist emphasis upon God’s relation to the world through covenant alone, he also has a quasi-Thomistic realism present insofar as God’s being-in-becoming, or the universal-in-the-particular can come to be known by the human agent as the human comes to participate in or becomes ‘a partaker of the Divine nature.’
I think that if the lineaments in my brief sketch hold up to any sort of scrutiny what we ought to realize is that Barth was genuinely engaged in what has come to be called ‘constructive theology.’ As Kenneth Oakes points out in his book Karl Barth on Theology and Philosophy, Barth was less stressed about fitting into this or that theological category, and more concerned with allowing the pressure of the Gospel itself to determine the shape of his theological articulation; even if that meant cross-breading various strands of the theological textus receptus as that presented itself to him in the Great Tradition and the Reformed scholastics he had knowledge of. This helps explain, at least for me, why Barth’s theology always tended to reify or reformulate what previously counted as classical theology. He was less concerned about meeting the expectations set out by the Church, and more concerned with meeting the categorical and conceptual expectations set out by the Gospel. He was a Free theologian, who thought under the freedom he believed Christ gave him as one set free, indeed, by the Son of Man: ‘for who He sets free will be freed indeed.’
I think Barth’s theology, like Luther’s, represents some of, if not the best of Protestant theologizing; precisely because they both were slavishly driven to their theological conclusions by following the Gospel itself. They did theology that was in protest to the magisterial norms that the scholastics felt compelled to follow previous. And this is why I am a hearty proponent of both of these theologians: as you work through their respective theologies you will be able to discern reference to the via antiqua and the via moderna, both; and of course other special elements as those were made uniquely available to them per the respective periods of history they inhabited. In the end, Barth and Luther, both, I maintain, were affected by the pieces of various theological (and philosophical) traditions, which is illustrated in the way they wrote theology such that they operated at almost naïve levels insofar that the conceptual grammars they deployed were second-fiddle to what actually mattered to them: which was bearing witness to Jesus Christ through the proclamation of the written and preached Word.
 Michael Allen Gillespie, The Theological Origins of Modernity (Chicago and London: The University of Chicago Press, 2008), 24.
 George Hunsinger, How To Read Karl Barth: The Shape of His Theology (New York/Oxford: Oxford University Press, 1991), 16-18.