Karl Barth was the greatest theologian since the Reformation, and his work is today a dead letter. This is an extraordinary irony. Barth aspired to free Christian theology from restrictive modern habits of mind but in the end preserved the most damaging assumptions of the ideas he sought to overcome. This does not mean he no longer deserves serious attention. Barth now demands exceptionally close attention, precisely because his failures can teach us how profound the challenges of modernity are for theology—and show us the limits of a distinctly modern solution to them.

My own interest in Barth was inspired by a conventional religious crisis and followed a recognizable script. As an undergraduate I was anguished to discover a conflict between the creed I was reciting in church and the arguments I was reading in Descartes, Hume, and Kant. Although my grasp of their arguments was imperfect, it seemed to me obvious that the Enlightenment philosophers posed a lethal threat to Christian belief. I found nothing alarming in their shallow accounts of the life of Jesus, the authority of the Bible, or the possibility of miracles. These I dismissed. But the modern consensus, involving thinkers of otherwise diverse views, that human reason could not attain genuine knowledge of God had become a source of debilitating dread.

Descartes instructs us to doubt everything except clear and distinct ideas, which turn out in the end to be few in number. Hume counsels that we restrict our knowledge to sense impressions of a material world whose causal regularities were largely imagined. Kant wants to transform speculative aspirations into an analysis of the knowing subject. Learning these things, I judged that modern philosophy imperils biblical religion not by elevating the power of reason—histories claiming so are gravely misleading—but by impairing our ability to reason properly about God. For if human knowledge is indeed limited to physical sense experience or to the categories of understanding imposed by the mind, one cannot speak credibly about the God of Christian doctrine.

As I soon discovered, however, initially with great relief, theological liberalism promised otherwise. We may be unable to reason directly about God, and in that sense the creed of my youth could not be affirmed in a traditional way, but it could nevertheless still be affirmed in an existentially meaningful way. A good deal of liberalism’s appeal, in fact, stemmed from the conviction that the Christian message could be genuinely personal.

A movement that had drawn some of Europe’s most gifted scholars over the previous two centuries, theological liberalism set its talents to securing articles of peace between an advancing modern worldview and a religious tradition in confused retreat. It adopted different strategies, but on the main question that disturbed my student slumbers—how my deepest convictions could be legitimately affirmed as true—the giants of liberalism agreed. They argued that if Christians would accept the limits on human reason imposed by the Enlightenment, believers not only would reap spiritual benefits but would encounter a purer form of Christian faith. Under the agreement negotiated by liberalism, Christian theology would cease defending truth claims about the order of nature and address instead the private faith of individuals or the moral good of secular society.

Two of Barth’s teachers provide examples. In the winter of 1906, Barth enrolled at the University of Berlin to study under Adolf von Harnack, arguably the preeminent academic in Wilhelmine Germany. Author of a major liberal historiography, History of Dogma (1894–98), Harnack was convinced that the teachings of Jesus had been distorted by Greek philosophy and could be recovered only through historical inquiry. Harnack invested scholars with tremendous authority, regarding the historical-critical method as part of the Reformation’s mission to return Christianity to its primitive essentials. He assured believers that modern thinking was an unambiguous blessing, as it could liberate them from a metaphysical mindset that was foreign to the original spirit of their faith. And that spirit was animated by a simple creed about the universal Fatherhood of God and his presence in every human soul.

Barth learned a similar lesson from Wilhelm Herrmann. A professor at Marburg, where Barth entered after leaving Berlin, Herrmann embodied the vibrant religious legacy of Kant, who had cautioned against the pursuit of unresolvable metaphysical questions. The “land of truth,” Kant warned, is a tiny island “surrounded by a vast and stormy ocean, the native home of illusion, where many a fog bank and many a swiftly melting iceberg give the deceptive appearance of farther shores.” Kant thought identifying reason’s “unalterable limits” portended not the end of religion but its ethical revival; the fact that the “starry skies above” were speculatively inaccessible meant human beings could now focus on obeying the “moral law within.”

Herrmann seized on Kant’s idea that religion was principally about morality and made truth claims fundamentally different from those of science. Theologians had wrongly thought that Christianity provided a privileged perspective on the physical world, a mistake the advance of the natural sciences could only expose to ridicule. But the uniqueness of Christianity was a matter of personal experience, not demonstrable knowledge. Herrmann argued that the Christian life involved communing with God’s spirit through the moral influences exercised by Jesus’s life on human history.

By uncoupling Christian theology from an outdated worldview, Harnack and Herrmann hoped that theology could better express the teachings transmitted by the biblical writers, a message allegedly free from a cosmology to which no intelligent person could assent. As Gary Dorrien writes in his excellent book The Barthian Revolt in Modern Theology (2000), Barth’s teachers thought Christian anxiety about modernity was misguided: “Harnack had assured [Barth] that liberal theology recovered the simple and beautiful religion of Jesus; Herrmann convinced him that liberal theology retained the essential gospel faith through its insistence that the living Christ could be known personally.”

Theological liberalism offered itself as a respectable way to preserve the culture, language, and ethics of Christianity without abandoning modern philosophy. There was much to admire in this tradition, and as a student I was impressed by its intellectual courage and institutional prestige. This was a route I might have taken had a perceptive teacher not handed me the first volume of the Church Dogmatics (1932).

In Barth I met a thinker who told me that liberalism was on a fool’s errand, offering a fraudulent solution to a misunderstood problem. Liberalism could not inoculate my faith against the challenges of modernity, because it misjudged the import of modernity for Christianity.

Barth wrote from a commanding position. He not only had lived through the rise and fall of European liberal theology but had directly influenced its changing fortunes. The defining events of Barth’s career occurred as a result of the First World War. After witnessing Christian support for German militarism and struggling as a pastor in a working-class congregation, Barth became convinced that the foundations of establishment liberalism, which had for a century supported the intellectual scaffolding of German culture, were irremediably corrupt. His ideas came together in an incendiary commentary, Epistle to the Romans, whose second edition, published in 1922, was famously said to be “like a bomb on the theologians’ playground.”

Barth’s genius was to have noticed that modern theology had effectively ceased speaking about God. It was not that God had disappeared from Western thought—he was, as it happens, being conscripted into an expanding number of new roles—but theologians were increasingly using God in order to explain or justify positions held on secular grounds. Sometimes the idea of God was discerned in the order of the natural world, at other times he was said to be the ground of moral obligation or the mystery of human subjectivity—in any case, God was used to sustain a secular scheme of knowledge. To satisfy his need for truth, Barth wrote, “man steps out in a bold bid for truth, creating the Deity according to his own image—and in a confident act of self-assurance, undertaking to justify and sanctify himself.”

Liberalism came in several varieties, but it consistently made two moves. First, often drawing on something like St. Augustine’s observation that the heart intuitively seeks God, it argued that religion or religious experience plays an integral role in our lives. Sometimes we hide this from ourselves, but an examination of our deepest commitments reveals an ineliminable religious dimension to human nature. Second, it argued that Christianity is the loftiest or most fitting historical expression of our innate religious impulses. The Christian proclamation could be deemed “true” because it corresponds to the religious needs of modern man.

Barth subjected to pitiless critique the idea that Christian theology could be developed around an interpretation of religious experience, famously saying, “One cannot speak of God simply by speaking of man in a loud voice.” In the seventeenth chapter of the Church Dogmatics, “The Revelation of God as the Abolition of Religion,” he presented his most searing criticisms. Barth did not so much deny human beings’ natural religiosity, which was so foundational for liberal theology, as give it a radical biblical interpretation. Yes, our hearts are restless, but left to themselves they rest before idols of our own making. The Bible unmasks all religions as the artifice of human presumption. “Religion is clearly seen to be a human attempt to anticipate what God in His revelation wills to do and does do. It is the attempted replacement of the divine work by a human manufacture.”

In equating liberalism with idolatry, Barth borrowed from an unlikely source. Ludwig Feuerbach’s The Essence of Christianity, treasured as much by Barth as by Karl Marx, advanced an ingenious argument in defense of atheism. A student of Hegel’s, Feuerbach adopted the assumptions of liberalism and regarded religious experience as the proper subject of theological inquiry. But rather than showing that Christianity expressed a human religious possibility, Feuerbach turned liberal theology inside out, concluding that God was the projection of man’s highest ideals. God is man writ large. Barth admired Feuerbach’s subversion so much that he often assigned him to students. He wanted them to appreciate that Feuerbach simply took liberal theology “completely seriously,” which could only mean “turning lovers of God into lovers of men.”

Here we reach Barth’s pivotal argument. God is not known through spiritual striving, moral reason, or historical experiences. God is known solely through God himself. Barth did not dispute that attaining knowledge requires attentiveness and diligent investigation. He only maintained that knowledge begins with objects of experience and that, since God is no mere object, our knowledge of God must conform to what he graciously provides. “True knowledge of the one and only God,” Barth argued in his Gifford Lectures of 1937 and 1938, “is based on the fact that the one and only God makes himself known.”

For Barth it was therefore misguided to reflect on God from a standpoint outside faith in divine revelation. This is a matter of intellectual precision, rather than special pleading. “If God really is God then to approach Him or even to consider that we can know Him in any way except out of Himself,” Barth insisted, “would be a form of irrationality.” Indeed, the attempt to do theology apart from revelation, as Barth said of the work of Schleiermacher, is “just one gigantic swindle.”

Barth’s appeals to revelation earned him a reputation as an opponent of modern thought. It was entirely undeserved. He made a tactical alliance with the Enlightenment on a key point: We are incapax Dei, lacking in speculative powers capable of reaching divine heights. Barth used this pact, however, to secure his claim that knowledge of God can come only from God himself. Barth was no reactionary. His arguments were almost always careful attempts to repurpose modern ideas for Christian ends. Modern people had demanded freedom for human self-expression, and Barth only asked that the same courtesy be extended to God.

This led him to ground his theology entirely within Christ, God’s self-expression in history. He claimed, perhaps uniquely, that “revelation does not differ from the person of Jesus Christ. . . . To say revelation is to say, ‘The Word became flesh.’” Through this seemingly brilliant maneuver, Barth recognized and at the same time bypassed the Enlightenment suspicion of speculative knowledge. Barth agreed with the Enlightenment insistence on the historical and empirical conditions of our knowledge, only to observe that God himself became historical and empirical. The Incarnation therefore moved past the critical arguments of Descartes, Hume, and Kant. For in Christ, God becomes present to us from within, from below, in flesh.

With this insight, Barth set off in a decades-long attempt to inscribe all Christian thought within “the strange new world of the Bible.” As even those who opposed the idea conceded, there was something captivating about his extravagant efforts to interpret everything in light of the biblical story of salvation. God’s intervention in history was not simply an epistemic bridge linking the human mind to God. Barth argued, with extraordinary narrative verve, that Jesus Christ is also the source, ground, and goal of all created being. This violated no Kantian or Humean stricture, nor did it require recourse to philosophical speculation. Barth was merely attempting to show how a contingent historical event, the life of a first-century Jew, could be recognized as the universal truth of all reality.

Barth was often hailed as a biblical theologian, but the truth is that he authored one of the great metaphysical treatises in modernity, treating the person of Christ as the ultimate cause and explanation of all things. Christology provided him exclusive access to the questions traditionally seen as falling within the domain of philosophy but now deemed to be speculatively off limits. He argued that in Christ and only in Christ can one encounter the true and the good, the intelligible form through which all things were made. In this respect his theology worked much like a more classical style of philosophy, invoking Christ to explore the “principles” or “beginnings” of things. “In the history of Jesus,” he wrote, “we have to do with the reality which underlies and precedes all other reality.”

Barth used the Enlightenment critique of reason to secure the absolute priority of revelation. But his concession came with a price, a cost he would increasingly pay in his mature work. Having rooted theology completely within Christology, he was required to claim that God and his revelation were somehow identical. Revelation is not, in other words, a side door through which God permits us an obstructed view of himself. God is one with his deed in salvation history. He is his revealed life.

In defense of this claim, Barth asserted that the reason that God can be present with humanity in time is that humanity is present in God’s eternity. This arresting belief that God is in some way human from all eternity—that humanity is eternally enclosed in the second person of the Godhead—is the core of Barth’s entire theology.

What did he mean? This remains a topic of debate two generations after his death in 1968. He began by stressing the irreducibly personal nature of revelation. This was another shrewd use of modern thought. Where liberal theologians had rooted all understanding in human subjectivity, Barth rooted all reality in divine subjectivity. The idea was that God’s entrance into salvation history is a dramatic performance of his very self, not an aspect or feature of his identity behind which his deepest nature remained hidden. One might say that for Barth God is absolutely truthful: He perfectly shows himself as himself.

While it is difficult to ignore the ambition of Barth’s theology, it is also difficult to overlook its flirtation with novelty. Barth never fully owned up to the radical implications of his identification of God with revelation. He sometimes suggested that God actually constitutes his divine identity in his act of self-disclosure. That would mean that God’s revelation is not simply a trustworthy expression of his nature but is integral to it. If the idea could be put starkly, God’s being is not merely a being-in-act but a being-in-this-act. He is a God who is not only made known through his words and deeds; he is a God who lives through what he says and does.

Barth had special reasons for identifying God’s essence with his revealed actions. Of all the modern critiques of Christianity, the accusation that God was an obstacle to human flourishing and happiness pained him most. He probably had a tendency to over-theologize, and he traced the roots of this view, which he believed lay at the origins of secular thought, to the scholastic separation of the question of God’s existence from that of his revealed identity. Barth held this distinction responsible for the suspicion that God’s freedom and power are not intrinsically tied to his gracious offer of salvation. So long as the question of God’s existence even in principle admitted of an independent, philosophical answer, modern people would be prevented from recognizing what Barth most wanted them to see: that God eternally wills the redemption of the human race through the person of Jesus Christ.

In his extraordinary 1956 lecture “The Humanity of God,” Barth made the daring argument that from the very beginning, from before the foundation of the world, God the Father intends fellowship with humanity through the man Jesus Christ. As he put it, God is the eternal “partisan” of the human race—not as a response to human sin, but as the first and original will of God. To modern readers who regarded Christianity as a distraction from pursuing human welfare, Barth therefore offered the story of a God whose eternal identity aims at the vindication of the human race. What takes place in God from everlasting to everlasting is nothing less than “the affirmation of man.”

At first glance, Barth orchestrates a stunning reversal. He allows modern philosophy to close off traditional paths to transcendence, but then exploits the vulnerability of philosophy to a God arriving in Jewish flesh. Yet Barth’s argument does not succeed, and its failure has the widest possible implications. Far from liberating theology from modern captivity, he leaves it trapped within the immanent confines of secular reason.

The mere suggestion defies both received wisdom and the canonical story of twentieth-century theology. Barth is widely acknowledged to be a defender of orthodoxy and is both praised and criticized for flouting the settled habits of secular thought. According to British theologian John Webster, Barth is “a central figure in the break up of the modern tradition,” a theologian whose “vigorous critique” of modernity exposed “its fatal weaknesses.” Barth achieved no such thing.

To understand his mistake and its ramifying consequences, we need to place his work within a broader historical context. Perhaps the best way to understand the spirit of modern philosophy is to see it as a dismantling of the classical understanding of God and the ordered cosmos it sustained. Classical theism names not only a way of thinking about God but a way of understanding the nature of the world and our place in it. Developed through common effort over centuries, it came to endorse a number of interlocking theses: that God’s essence is identical with his existence, that nature is governed by an act of divine intelligence and love, that rational beings find fulfillment in learning the truth about God, and that all knowledge is grounded in God’s self-understanding.

Part of the achievement of classical theism was to demonstrate the interdependence of these positions. Deny divine simplicity, and God’s proper relation to creation is dissolved. Deny that creation exists by participating in God, and its intelligibility is diminished. Deny that human beings naturally desire beatitude, and the moral law is obscured.

Modern philosophy assumes the falsity of classical theism. It begins by discarding, not disproving, the family of arguments that provide the metaphysical grammar of Christian orthodoxy. Barth followed suit—and the results were fatal.

Barth yielded to modernity’s most pernicious idea, which took aim not at belief in the supernatural but at our rational capacity for knowledge of it. In denying what Jesuit philosopher Bernard Lonergan called the “native infinity” of human understanding, Barth capitulated where he most needed to take a stand. He seemingly did not understand that restricting reason was modern philosophy’s great act of presumption, not humility. Nor did he understand that rejecting the secularity of reason was Christian philosophy’s great act of piety, not hubris. And his bargain with Kant—turning the limits of reason into an opening for revelation—could only corrode the foundations of Christian faith.

By rejecting the speculative power of the intellect, Barth was drawn into making two mistakes. First, he turned his back on the metaphysics of classical theology, rendering almost unintelligible the conceptual idiom of the doctors and creeds of the Church. Barth did not hide this, and he worked hard to square his dogmatics with Christian tradition, replacing appeals to nature and causality with appeals to history and narrative, but the result was that he could not properly and consistently distinguish God’s nature from his actions in the history of salvation.

Barth’s second and deeper mistake was to sever the mind’s speculative relation to God. He dissolved the classical synthesis of faith and reason, collapsing all theological understanding into an exercise of faith. Unable to appeal to truth besides Jesus Christ, Barth was powerless to explain how truth could be known and communicated without supernatural assistance. He was even pressed to invoke divine revelation as proof of the existence of the external world, a sign something had gone very wrong.

His basic error is evident in his rejection of natural theology, which holds that careful observation of contingent beings can disclose the necessary being of God. This argument comes in several permutations, most of which are sketched by Thomas Aquinas, but its success in demonstrating God’s existence was arguably a secondary concern. The primary purpose of traditional natural theology was to show the indissoluble connection between the human intellect and a transcendent God who is Being itself.

Barth’s charge that some natural theologies compromised divine transcendence was true enough, but his indictment was indiscriminate. He did not appreciate that classical natural theology aimed at clarifying the proper reach and function of natural reason: that we can know with certainty that God exists but cannot understand his divine essence in itself. This teaches us both the nobility of reason (knowing that God is) and its radical insufficiency (not knowing what God is).

He simply could not allow that a genuinely philosophical understanding of God is demanded by the intellect’s desire to know. He wanted to sharpen his dispute with classical theism so as to make it entirely about the revealed nature of God. But this could not succeed, if only because what one holds about God is informed by a host of philosophical commitments. For its part, classical theism maintained that Christian belief both presupposes and propels philosophical inquiry. It acknowledged, even celebrated, that Christian belief is committed to philosophical positions concerning the intelligibility of the natural world, the power of the human intellect to understand that world, and our capacity to communicate truth. (Hence the First Vatican Council’s condemnation of those who denied that God can be known with certitude by the natural light of human reason.)

Why did Barth fail to see the theological necessity of metaphysical inquiry? His idée fixe—that God is wholly identical with his self-enactment in history—stood in the way. There can be no natural knowledge of God, after all, if God lives in and through his self-revelation. In passages wincingly difficult to read, he sometimes took to mocking natural theology and classical theism, suggesting that they bore witness to a demonic power rather than a God who lives in covenant relationship with humanity.

There is much of lasting importance in Barth. One can find contributions to Christology and trinitarian theology that surpass almost everything written in the twentieth century, as well as a meticulous cataloguing of the history of Protestant scholasticism. He never spawned vulgar popularizers, and to this day Barth scholarship has a well-deserved reputation for its exceptional quality and academic sobriety.

But we are living through the unraveling of the Christian metaphysic, which began with a rejection of classical theism, proceeded to abolish purpose from the material world, and is now eliminating the rational and moral nature of man. In order to recognize this metaphysical demolition for what it is—one can scarcely repair what one misunderstands—Christians are no more helped by Barth than by theological liberalism. Both collude with secular reason in denying our capacity to attain knowledge of the highest things. We will be immeasurably better served by recognizing, as John Paul II wrote in Fides et Ratio, that our “crisis of meaning” stems from failing to defend the ability of reason to know “the ultimate and overarching meaning of life.”

Matthew Rose is director and senior fellow at the Berkeley Institute. He is the author of Ethics with Barth.