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What Happens When a Theologian Uses Heidegger? Dietrich Bonhoeffer’s Heidegger

Fundamentally, secular and religious minds face a singular philosophical problem — the problem of knowledge. Regardless of how one answers the question of God’s existence, asking and answering questions of moral importance requires grappling with how individuals relate to knowledge. This in turn brings up lines of inquiry surrounding the nature of reality itself and how the human mind relates to external truth.

In Dietrich Bonhoeffer’s Christological Reinterpretation of Heidegger, Nik Byle successfully shows how Bonhoeffer repurposed the best of secular philosophy for theological use. Byle offers a deep, well-researched contribution to the literature surrounding the work of Bonhoeffer. Although focused primarily on Bonhoeffer’s analysis of the problem of act and being, this book provides Christians and non-Christians alike an example of how philosophy and theology can productively interact with foundational problems of human existence, all while remaining committed to mutually exclusive truth claims.

Problem of Knowledge

In meticulous fashion, Byle describes how Bonhoeffer engaged with secular philosophy – specifically Heidegger – by detailing Bonhoeffer’s approach to the problem of knowledge, his nuanced rejection of competing theological dogmas of the time, and the criteria he developed to determine the validity of secular and theological answers to the knowledge problem.

Bonhoeffer formulates the problem of knowledge as a problem of act and being. Acts are concrete, discrete, and momentary, while being is characterized by continuity across time. Under this approach, Bonhoeffer analyzes the validity of philosophical systems based on their ability to mediate and coordinate between act and being. Overemphasizing either act or being in philosophy leads to grave error.

Act-based philosophies risk reducing human personhood to nothing more than a succession of conscious decisions. Theologically, this strips revelation of its meaning by reducing God’s divine plan to a series of discrete actions. Revelation of this nature removes the preconditions necessary for Christian identity to exist over time. If revelation were simply a series of separate actions, then the continuity of Christian knowledge and identity breaks down because its relationship with time is disconnected and disjointed rather than intricate and preordained.

Thus, being-oriented aspects of philosophy are essential because they provide the continuity over time that act-based philosophies lack. However, being-oriented philosophies have problems of their own. For example, Bonhoeffer’s critique of Hegelian idealism centers on the detached nature of his philosophy. A being-oriented philosophy that fails to deal with life as it is actually lived loses the necessary element of concreteness that is the best of act-based philosophical thought.

Bonhoeffer explores this fundamental problem in depth in his post-doctoral thesis, Act & Being. In this thesis he tackles questions of Christology related to how time works in relation to the temporal (concrete) versus the continual (being). In so doing, he shows how – at the deepest levels – secular philosophy and religious theology wrestle with the same questions. He also builds a bridge between the secular and religious worlds by showing how philosophical concepts, although inherently flawed due to lack of divine revelation, are useful in theological analysis.

Thus, by giving credit to secular ideas when earned, Bonhoeffer can show the reasonable nature of applying theological solutions to existential problems.

Bonhoeffer’s Rejection of Competing Theological Schools of Thought

Before addressing Byle’s analysis of Bonhoeffer’s engagement with secular philosophy, Heidegger in particular, the author identifies a crucial biographical aspect of Bonhoeffer’s theology. An early indication of Bonhoeffer’s unique approach to the problem of act and being is his rejection of two competing theological traditions of his time. As a theologian of the early to mid-20th century, Bonhoeffer was the “academic child” of two warring theological factions. These factions, liberal and dialectical theology, answered a fundamental question in a mutually exclusive manner. The central issue dividing these two schools was revelation’s relationship to time and history and the corresponding nature of the theological method that arises from any given answer to the question.

Liberal theologians, exemplified by Adolf Von Harnack, viewed critical-historical study as the “only means” to properly understand theological reality. On the other side of the dispute were dialectical figures, such as Karl Barth. Under the Barthian view, there is a fundamental distinction between understanding Christ during the brief period in which He took human form and any other time during human history. Those who favored this approach believed Christ’s resurrection and subsequent ascension rendered Harnack’s critical-historical approach useless because Christ can no longer be known “according to the flesh” and thus the historical lens fails to properly elucidate the nature and being of Christ.

Bonhoeffer rejected the conclusions of both schools of thought, viewing them as guilty of distinct flaws. Harnack’s approach risks making Christ nothing more than an object of human study, indistinct from other historical figures, while the Barthian position risks detaching Christ from the reality of the present moment, thus destroying essential elements of Christian identity. How can Christ, the Immanuel – God with us – be so removed from the human experience?

Rather than placing himself in either of these camps, Bonhoeffer instead seeks out an alternative answer. His rejection of these warring theological camps is mirrored in his critiques of secular philosophers, who he views as offering incomplete answers to the problem of act and being.

Bonhoeffer’s Criterion for Completeness

As Byle documents, Bonhoeffer adopted multi-faceted and complex views surrounding any possible solution to the problem of act and being. Bonhoeffer identified three conceptual levels that must be addressed if one is to successfully mediate between act and being. These conceptual levels are the epistemological, anthropological, and theological.

This criterion arose from Bonhoeffer’s rejection of what he believed to be a Descartes-driven fixation on epistemology. This obsession, he argued, necessarily results in a fundamentally flawed theory of knowledge because it places the cart before the horse. Placing epistemology at the foundation of a knowledge theory’s hierarchy fails to account for the necessity of anthropology. Any such theory is fatally flawed because it fails to account for human existence itself in real, i.e. historical/cultural, terms. Therefore, an answer to the coordination problem between act and being concepts must be rooted in a correct anthropological understanding of human life.

Although this criterion is complex, it still fails to account for the degree of nuanced embodied in Bonhoeffer’s writing on possible solutions to the problem of act and being. In addition to the three criteria listed above, Bonhoeffer’s praise and critique of various philosophies discussed four distinct but interrelated, sub problems that must be addressed in by anyone seeking to mediate between act and being.

Despite the fascinating nature of Bonhoeffer’s discussion of these sub criteria (transcendence, boundary, continuity, and concreteness), for the sake of limited time and space, these sub problems will only be discussed in relation to Bonhoeffer’s engagement with Heidegger’s work.

Bonhoeffer’s Engagement with Heidegger

According to Bonhoeffer, Heidegger’s philosophy is successful in coordinating the problem of act and being at the anthropological level. This success comes in the form of Heidegger’s concept, Dasein. On the flip side, Heidegger’s failure relates to his inability to meet the sub criteria of transcendence. Byle presents a comprehensive and compelling description of Bonhoeffer’s analysis.

The concept of Dasein effectively coordinated the problem of act and being because (1) it is rooted in an anthropological understanding of theories of knowledge, (2), its description of “thrown projection,” and (3) its temporality.

Heidegger’s Anthropological Understanding of Knowledge

Heidegger’s views of ontology drive his creation of Dasein. To Heidegger, a foundational question any theory of knowledge must answer is, “what is the meaning of being in general?” Any reasonable answer to this question requires an epistemology. However, this epistemology does not stand on its own. Instead, it is dependent on pre-ontological assumptions about reality. Therefore, to understanding being cannot be investigated directly, instead the inquirer must “go through” some external entity to understand being. This entity is Dasein.

In essence, Dasein is the precondition that makes ontology possible. In this way, Dasein is temporal and deeply anthropological. Dasein’s pre-scientific engagement of the world is critical to Bonhoeffer’s understanding of Heidegger. Dasein is a solution to the act/being problem because it is the foundation of understanding. One cannot clarify human existence without understanding Dasein. Thus, epistemology is properly rooted in anthropology.

Dasein & Thrown Projection

Heidegger meets Bonhoeffer’s criteria of continuity through his understanding of the existential structure of reality. In his philosophy, “worldhood” is the structure of existence allowing for any given environment. Thus, worldhood represents the possibility of any number of realities, i.e., an individual may be in the “world” of the classroom, the home, the theater, etc.

Thrown projection describes the relationship between reality and time by acknowledging that Dasein always finds itself within a specific context or “world.” Because of the inherently interconnected nature of being (i.e., its continuity), worlds are not truly “created” by one singular subject. Rather, each person finds himself “thrown” into the shared network that constitutes social meaning. Individuals can neither escape their pasts, nor are they defined by it. Instead, all human action is predicated on the infinitely complex interplay between choice and possibility. Everyone is bound by possibilities and yet creates by transforming possibilities into concrete realities.

This fits with Bonhoeffer’s understanding of reality because it posits that a proper understanding of human existence is found in both act and being. Bonhoeffer described Heidegger’s success by saying he “has succeed in forcing together act and being in the concept of Dasein; both what Dasein itself decides, and the fact that it is itself determined, are brought into one here.”

The “thrown projection” Heidegger discussed cannot be properly understood apart from his analysis of the inherently temporal nature of human existence.

Dasein’s Temporality

Heidegger understood temporality as a process that is embodied in the phrase “temporality temporalizes.” Byle breaks this complex phrase down by describing it as “the pressing forward into the future while, simultaneously and based on that pressing forward, the pulling up of the past.” This means temporality cannot be understood as a singular entity, such as past, present, and future.

Instead, temporality’s structure mirrors that of thrown projection. As possibilities are actualized in both the proximal and distant dimensions, temporality and thrown projection unfold simultaneously. When expressed through history, these twin processes constitute what is colloquially described as “destiny” or “fate.”

Bonhoeffer sees a useful theological application of this understanding of temporality. By applying the same structural analysis of temporality and thrown projection to the concept of eternity, Bonhoeffer draws God into time. Understanding Heidegger’s Dasein as “constant decision-making and, in every instance, already being determined,” allows Bonhoeffer to conceptualize a constructive relationship between eternity and time.

This is critical to Bonhoeffer because Heidegger’s framework gives him useful theological tools with which to explain Christ’s and the Church’s relationship to time, a relationship which is both temporal and continual.

Authenticity: Dasein’s Failure

Bonhoeffer’s critique of Heidegger relates to his understanding of cor curvum in se, or the idea that human existence is understood according to self-reflection and the human capacity for reason. This reasoning conflicts with Bonhoeffer’s view of the necessity of Christ’s revelation to man, and his belief that truth cannot be found absent an external, Kantian “thing in itself” to which the human being relates.

Central to Heidegger’s philosophy is the idea of the authentic, or owned, self. Essentially, authenticity occurs when Dasein projects itself towards death. The struggle with anxiety about existing in the world is a consequence of Dasein encountering conscience and becoming aware of the natural human tendency to avoid self-awareness. By “owning” itself through the adoption of responsibility, Dasein runs towards death, yet becomes free to genuinely choose between the numerous possibilities available to humanity.

Bonhoeffer rejects this concept of authenticity because, in his view, it remains tied up in cor curvum in se (sin) through its rejection of the necessity of divine revelation. Because Heidegger’s Dasein moves into authenticity, its conscience becomes both the “accuser, accused, and judge.” This means Dasein is self-justifying, saving itself from its own existence. This means it has turned in on itself, resulting in flawed, circular, and egotistical reasoning. Bonhoeffer’s understanding of the necessity of God and the essential role of Christ as the mediator between humanity and truth causes him to reject this view.

However, despite Bonhoeffer’s rejection of Heidegger’s concept of authenticity, this does not stop him from salvaging aspects of its philosophic value. Rather, he takes the concept of authentic Dasein to distinguish between “in Adam” and “in Christ” existence. To be “in Christ” is to decide as to the person of Jesus Christ, which is an action upon human Dasein. This action then necessitates a place of being in the world, through participation in the church, the preaching of the Word, and engagement with the sacraments.

However, because the decision to act in relation to Christ is built on an individual’s divinely inspired being that is receptive to the revelation of Christ, members of the Church are simultaneously the subjects and objects of action. Therefore, “in Christ” existence mediates between act and being. The same is true of “in Adam” existence, only in reverse. The non-Christian has not been acted upon, i.e., is not receptive to the revelation of Christ. Without this necessary precondition, the non-Christian does not believe and remains in this distinct existential mode of being.


Byle shows how Bonhoeffer utilizes his engagement with secular philosophy – Heidegger in particular – to engage in Christological analysis. Because Bonhoeffer is open to the use of the best philosophy in theological reasoning, he identifies and grapples with the same questions as his secular counterparts. Unlike other theologians, Bonhoeffer’s work is remarkably broad in scope, covering questions of metaphysics, existentialism, and ethics. This breadth makes his work difficult to interpret but gives his body of literature a depth and texture often lacking in theological spaces.

While some theologians focus on a strict defense of the Christian faith, or answer technical textual questions, Bonhoeffer instead dives deep into the waters of philosophy, seeking to answers to impossible questions, such as the nature of how time and space interact. Bonhoeffer then applies this knowledge to theological questions of Christology.

In this way, Bonhoeffer operates from a set of common Christian assumptions. Having accepted orthodox Christian claims as true, Bonhoeffer turns his attention to the implication of these truths. In his engagement with secular philosophy, he borrows the best of philosophic thought to elucidate theological truths. This unique theological approach builds a bridge between the secular and religious, providing an avenue through which religious and secular minds can better understand one another.

Dietrich Bonhoeffer’s Christological Reinterpretation of Heidegger
By Nik Byle
Lanham, MD: Lexington Books, 2021; 240pp

Originally published in the Voegelin View.