The Usefulness of Philosophy for Theology: Foundational Concepts and Definitions

Paul Maxwell, Ph.D.

Paul Maxwell, Ph.D., writes about theology, mental health, marketing, and fitness. Paul has been writing on for over a decade.

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*I wrote this content for my introductory lecture when I taught Introduction to Philosophy at Moody Bible Institute from 2014-2017.

Here, we will unpack some foundational concepts that will help us better understand the nature of systematic theology, and consequently to better understand the concept of the Trinity.

Foundational Concepts for Understanding Systematic Theology

Before we dive too deeply into theology, it is first necessary to understand the critical component components that make its very existence possible.


Theology is derived from the Greek terms theos and logos. Theos is the Greek word for God, and logos is the Greek word for word. So, theos-logos—theology—is simply a collection of words about God. Throughout church history, these words became more and more nuanced, and it became its own academic discipline—to study, and to speak about, as excellently as possible, who God is, what he has done, and what he has said.

Whatever insights we have about God can be applied to the world. Even atheists have a theology, but it’s just three words: “God doesn’t exist.” But of course, atheistic theology doesn’t stop at those three words. Friedrich Nietzsche, a 20th century German philosopher, pronounced that the world at his time had so far moved beyond the concept of God that it had lost its moral footing.

Understand ethics, ultimate reality, and theology through a biblical lens.

Nietzsche coined the term “God is dead”—in German, Gott is tot.

This phrase is often misinterpreted to mean: “God doesn’t exist.” But Nietzsche was saying quite the opposite. He was lamenting the death of God in the hearts of German philosophers who insisted on a version of objectivity, a worship of science, and a moral arrogance that led them to think they no longer needed God. But Nietzsche knew that without God, all of the philosophy we received, which stood on the ground of assuming that God does exist, would be lost.

Nietzsche’s full quote is this:

“God is dead. God remains dead. And we have killed him. How shall we comfort ourselves, the murderers of all murderers? What was holiest and mightiest of all that the world has yet owned has bled to death under our knives: who will wipe this blood off us? What water is there for us to clean ourselves? What festivals of atonement, what sacred games shall we have to invent? Is not the greatness of this deed too great for us? Must we ourselves not become gods simply to appear worthy of it?”

This is a very Christian comment, though Nietzsche himself was not a Christian. Nietzsche saw that what we believe about God determines what we believe about anything. And he also understood that what we believe about God is no small matter. Where God goes, morals go. Where God goes, values go. Where God goes, culture goes. And so, this understanding of theology gives rise to the adjective theological.

This term theological indicates that what we believe about God also extends to our whole lives. A theology of disability draws upon theological insights to inform how we should treat those with disabilities. A theology of political science will draw upon a theology of mankind and his revelation in Scripture to construct a proper understanding of how to act in our modern age.

So, theology is the study of God, his actions, his words, and the relevance of his person, actions, and words to our lives.

Systematic Theology

Systematic theology is the organization of that study into stable concepts that don’t change throughout the history of revelation, and will never change. In other words, systematic theology seeks to construct the most coherent, smooth information architecture that organizes what God says about the nature of the world .

Major topics within systematic theology are theology proper (the doctrine of God), soteriology (the doctrine of salvation), ecclesiology (the doctrine of the church), anthropology (the doctrine of man), eschatology (the doctrine of the last things), bibliology (the doctrine of Scripture), and hamartiology (the doctrine of sin).


Exegesis is the technical science of reading a text of Scripture. It’s a Greek construction (ἐξήγησις, exegēsis) that means “to lead out”—in a textual context, it means “to lead out the meaning. It’s the opposite of eisegesis, which means to lead in—eisegesis would occur when a reader inserts his own meaning into the text. Exegesis occurs when the reader seeks to understand what the author himself is saying.

Faithful Christian exegesis seeks to find what the text of Scripture is saying on its own terms, and then to do theology from there, rather than to bring a theological idea to the text of Scripture and try to shoehorn it in. Systematic theology, at its worst, does this quite often. It uses Scripture like a junk drawer and builds these conceptual skyscrapers with cheap exegetical material. But systematic theology at its best is self-evidently built upon good exegesis. The exegesis is itself part of the theological reasoning, not just a footnote.


Hermeneutics is, most basically, the study of interpretive methods. But more deeply, it is the science of extracting truths, values, significances, and applications from texts and applying them to other contexts. Exegesis is the first step of a good biblical hermeneutic.

Exegesis is isolated to a single text, but hermeneutics allows the reader to connect texts together to trace a literary theme throughout the entire canon of Scripture (a practice we call “biblical theology”) and to build conceptual models which grasp the truths God seeks to express (a practice we call “systematic theology”).

It’s important for us to have these concepts in our back pocket as we move forward—theology, systematic theology, exegesis, and hermeneutics.

Why Philosophy Can Help Us

It will be helpful for us to understand one more term as well—philosophy.

As we seek to better understand theology, and better understand the Trinity, it is important for us also to take seriously what philosophy can offer us. Generally, philosophy seeks to do what systematic theology does without Scripture. But that doesn’t have to be a bad thing. If systematic theology is the most excellent, nuanced way to make sense of what the Bible teaches, then philosophy is the most excellent, nuanced way to make sense of what common sense teaches us. And both of these disciplines, at their best, work in harmony. They inform one another. There are a few ways that philosophy can be helpful for theology.

Philosophy can help us make sense of Scripture by giving us concepts and tools to better put together what it said. Example: Calvin’s education as a humanist made his commentaries the first commentaries that are still usable today by pastors who use the grammatical-historical method of interpretation. Even The Apostle Peter admitted that Paul’s writings were hard to understand for the early church (2 Peter 3:16). Philosophy was one of the tools they used to make sense of those writings.

Philosophy can help us guard against heresy. The Nicene fathers used philosophy to fend off heretics. When they preserved for us the formula “One God in three persons,” this was a precise theological formula meant to guard against two incorrect theologies.

Philosophy can be a great enemy to the Christian faith—and it can be a great defense against those enemies. The better we understand it, the easier it is to dismantle criticisms of the Christian worldview. When a postmodernist critiques Christianity, we can respond that it is not only critiquing Christianity, but all commonsense worldviews that believe in truth, which is absurd. When a materialist like Richard Dawkins critiques Christianity as a myth, we can respond that he is actually critiquing all worldviews that believe in value, which is absurd. The better we understand philosophy, the easier it is to disarm those attacks. The easier it is to disabuse them of the notion that they are sophisticated.

Many people have difficulty getting their arms around what philosophy really is. That’s why here, I’m going to explain to you the entire history of philosophy in 6 simple terms.

The Entire History of Philosophy 

 I’m often intimidated by philosophical knowledge. People name drop philosophers and ideas with such fluency that I often feel like an idiot. Even after teaching philosophy at the college level for years, I am still insecure about my philosophical knowledge. But one thing that has always succeeded in making sense of unknown figures in philosophy is my basic conception of the story of philosophy. It is a very simple story, and can be explained without footnotes or block quotes. If you can memorize this simple story, you will be able to locate and plug-and-play any unknown or obscure philosopher.

The Three Fundamental Categories of Philosophy

The three fundamental categories of philosophy are metaphysics, epistemology, and axiology. Every single philosophical concept falls within these three domains, or somehow relates these three domains to one another.

Metaphysics is the study of ultimate reality. If physics studies what is true of the material world, metaphysics is a way of describing the immaterial world which gives shape and order to the material world. For example, the claim that the soul exists is a metaphysical claim. More basically, the claim that the world exists according to the laws of logic is a metaphysical claim. Metaphysics is the study of ultimate reality. It explains not merely the material, but the conditions in which a material world could exist.

Epistemology is the study of knowledge. Epistemology is the study of what we can know, how we can know things, and right and wrong ways of knowing. For example, logic and evidence are two kinds of epistemology. If you combine them together, you get the scientific method. The charge: “You’re being irrational” is an epistemological accusation. Atheism is a metaphysical claim (“God doesn’t exist”), and agnosticism is an epistemological claim (“We can’t know if God exists”).

Axiology is the study of value. Within axiology falls sub-disciplines such as aesthetics, which is the study of beauty and ugliness, and ethics, which is the study of right and wrong. Unlike metaphysics and epistemology, which are black and white categories, axiological realities can be measured in degree. So, a metaphysical claim such as “The soul exists” is either true or it’s not. The epistemological claim “You’ve committed a logical fallacy” is either true or it’s not. The axiological claim, “This painting is beautiful” or “You should have done better” are statements of relativity and degree.

The object of metaphysics is ontology. This word comes from the Greek word ontos, which means “being” or “substance.” So, ontology is the study of being itself. When we talk about the ontological aspect of something, we are talking about the existence of a thing in contrast to its epistemology or axiology—meaning, when we talk about the ontological quality of a chair, we are talking about the existence of the chair, not how we know it’s a chair or the value of the chair. Ontology sounds very much like an identical synonym with metaphysics, but metaphysics refers to ontology in distinction from physical claims.

In summary, a metaphysical claims refer to something distinctly transcendent above the physical, and ontological claims refer distinctly to the existence of a thing, not how it’s known or what its value is. We could take me, Paul Maxwell, as an example. When we talk about my ontological qualities, we talk about everything that makes me what I am—metaphysical and physical. When we talk about my metaphysical qualities, we are talking about my soul, my mind, my deeper qualities that aren’t scientifically quantifiable.

Every philosophical idea is either a metaphysical, epistemological, or axiological idea.

The Three Acts of Philosophical History

The history of philosophy is a history of relating three ideas in three acts—these three acts can be called Premodernism, Modernism, and Postmodernism.


Premodernism begins all philosophical thought with metaphysical claims. Epistemology was determined by the nature of metaphysical reality. For example, the first philosophers—the Presocratics, who came right before Socrates in the 7th and 6th century BC—they made very elemental claims like “All is water” and “All is fire.” What they meant by statements like this was something metaphysical.

The Presocratics were composed basically of two schools—The Eleatics and The Milesians. The Milesians emphasized the disorder and chaos of the world, and the Eleatics emphasized the orderliness and oneness of the world. Accordingly, the Milesians, because they saw the metaphysics of the world as chaotic emphasized sense experience as the proper epistemology, whereas the Eleatics, emphasizing the orderliness of the world even to the point of rejecting that change was real, saw reason as the proper epistemology. The Milesian philosophy emphasized change, or metabole, and the Eleatic philosophy emphasized unity, or logos.

Socrates then came on the scene and taught the world to ask bigger, better questions about reality. Instead of asking, “What is the right thing to do?” a philosopher should ask, “What is goodness?” In a sense, Socrates taught the world to think “meta” about realities—to conceive of the immaterial realities behind our operational use of certain concepts. Socrates pushed for conceptions of important realities that could be justified and universally applied without exception.

Socrates’s student, Plato, took this notion of “thinking meta” and applied it to the entire world. His claim, following the Eleatics, was that the material world was less real than the ideal world—in fact, it was only the world of ideas which was real; the material world was just a shadow of this idea world, since ideas are incorruptible, unchangeable, and fixed, while the material world fades and disappears. Plato called these ideas “forms” and defended the notion that we must access this “world of forms” through reason, and that right reasoning was the necessary path to live in the real world.

Plato’s student Aristotle argued against Plato. Aristotle argued that forms don’t exist in some separate reality, but exist in the material things themselves. In other words, the metaphysical world isn’t “up there,” but “down here.” Take, for example, the metaphysics of a human being. Is the substance of a human being an abstract idea that a human needs to conform himself to through reason? Or, is it an intrinsic potential that he needs to fulfill in order to be his best self? Plato would say that the idea “human being” is a form to which a human should conform himself. Aristotle would say that a “human being” is a substance that contains both form and matter which dictates proper action in order to fulfill its maximum potential.

Aristotle’s metaphysical shift changed the way he viewed ethics. Acting ethically for Aristotle was not conceived in terms of conforming yourself to some abstract form of justice, as Socrates had suggested. Instead, for Aristotle, ethics was conceived as a balanced expression of certain virtues which were inherently fitting to human nature. For example, take the act of facing danger. If you shy away from danger, you’re a coward, which is a vice. If you always rush headlong into danger, that’s foolishness. But if you tactfully and strategically engage danger—not shying away or rushing in, that is balance, and therefore is a virtue.

Christianity was heavily Platonic at its birth because the Platonic notions of abstract forms correlated well with Judeo-Christian speech about the incorruptibility of the divine essence. Platonic language served the early Christology debates very well as it sought to articulate a balanced Christology. It was through Augustine that Plato became the ruling architecture of Christian doctrine for the next millennium.

A millennium later, Aristotle made its way back into the West after his writings had been preserved by the Muslims. Philosopher Thomas most popularly used Aristotle as a framework for articulating Christianity, and the sophistication of Aristotle’s conception of substance allowed Christian doctrine to exit the realm of abstraction and begin making more sophisticated formulations about both the spirituality and the materiality of Christianity.

All of these philosophers have in common a premodern architecture—the first thing they do is posit the nature of the metaphysical world, and afterword ask how epistemology conforms to that metaphysic.


Modernism prioritizes epistemology over metaphysics. This is called “The epistemic shift.” This “epistemic shift” is sometimes historically called “The Enlightenment”—enlightenment being defined as thinking for oneself rather than speculating about substances and forms. Modernism, in the Enlightenment, is when philosophy started thinking primarily about method, and not so much about “ultimate reality.”

This epistemic shift occurred first in the philosopher René Descartes in the 17th century, who doubted all metaphysical knowledge. He asked: “What happens if we doubt everything? That’s the only way we could be certain of anything—is to mercilessly prosecute and doubt every single thing.” What is the end of this doubt? A simple proof—that even doubt is a thought, which means that even if you doubt everything, you’re still thinking, which means that the act of thinking can’t be doubted—therefore, the human mind exists. And he uses logic to construct an entire philosophical edifice without any religious or metaphysical speculation of premodernism. So, if the premoderns conceived the world in terms of the phrase, “I am. Therefore, I think,” it was Descartes who flipped everything on its head and argued: “I think. Therefore, I am.”

David Hume, an 18th century philosopher, took Descartes’s radical doubt to the next level. He made an important distinction between impressions and ideas. Impressions are experiences of the world—if I see an 8 ball on a pool table, that 8 ball makes an impression on my mind. If I see a cue ball on the same pool table, that cue ball makes a separate impression on my mind. If I see someone hit the cue ball into the 8 ball, and I witness the 8 ball move, Hume argues that I impose the idea of causality onto the relationship between the cue ball and the 8 ball. In Hume’s view, I am justified to believe that the cue ball and 8 ball are both real, but I am not justified in saying that I “know” the cue ball caused the 8 ball to move, because causality isn’t an object in the world that can make an impression on my mind.

Hume also classified morality as an idea, and infamously declared: “Is doesn’t entail ought.” In other words, you can’t deduce any binding moral principles from the bare material world.

Descartes’s philosophy is called rationalism because he builds an entire worldview based on a modernist conception of reason, meaning that reason as a way of knowing is the foundation of all justified knowledge. Hume’s philosophy is called empiricism because he builds an entire worldview based on a modernist conception experience, meaning that experience as a way of knowing is the foundation of all justified knowledge.

Immanuel Kant, several decades after Hume, attempted to reconcile Descartes’s rationalism and Hume’s skepticism. Kant argued that we need to make a distinction between what he called noumena and phenomena. The noumenal world represents the world as it really is (the world of ideas, in Descartes), and the phenomenal world represents the world as it exists in our perception (the world of impressions, in Hume). So, if a tree falls in the woods, and nobody is there to witness it, did anything happen? Noumenally speaking, yes it did—phenomenally speaking, no it did not.

We only have access to the phenomenal world. But there is a mechanism in our mind called “the transcendental” which translates the noumenal realm for us and displays the phenomenal world in our perception like a movie projector. To use another metaphor—think of the transcendental as a sausage maker. Imagine the noumenal world is the raw material of sausage, and the phenomenal world is the processed, packaged sausage link. Now imagine you go to a grocery store and read on the label that the sausage is made of the highest quality pork, and it’s organic. You try to visit the sausage factory to verify that the sausage is organic and that the materials are high quality, but they won’t let you in for security reasons. That seems understandable to you, so you decide to trust the sausage company.

Kant argues that we need to take the same posture toward the transcendental—we will never have justified knowledge of the world as it really is, and in that sense Hume’s critique of Descartes is correct (since all we have is our sense experience), but we should trust that what the transcendental gives to us in the form of the phenomenal world is practically true, and therefore while we may not be epistemologically justified in assuming that our claims about the phenomenal world translate to the noumenal, we are practically justified in assuming that the laws of logic can establish common rules of perception that govern everyone’s mind, and therefore work as common rules which human beings are justified in taking for granted.

Kant likewise attempts to rectify Hume’s moral crisis by proposing what he calls the categorical imperative—which is the notion that a moral law is binding if it can be universalized. For example, lying is categorically wrong because if everyone lied all the time, there would be no such thing as truth-telling, and therefore no such thing as lying. Therefore, lying should be morally wrong because to universalize it would be to destroy it. Same thing for adultery and murder.

Georg Hegel came in the 19th century to critique Kant—his basic critique is that Kant’s noumenal/phenomenal distinction doesn’t actually solve the disagreement between Descartes and Hume, but fortifies it. It traps people in the phenomenal and locks them out of any justified knowledge of the noumenal world, or the “real” world. So Hegel argued that ultimate reality makes itself known to the world through rationality. But the way it makes itself known is unique to Hegel.

Hegel argues that rationality ushers the noumenal world into our phenomenal world progressively through dialectic. What this means is that one generation of humankind may hold to a particular idea. That idea could be called a “thesis” about the way the world works. Then, the next generation rebels and comes up with an opposing idea. That idea is called an “antithesis.” The third generation rebels against the second generation and combines the strengths of both theses into a synthesis. Then, the fourth generation rebels against the third generation and the third generation’s synthesis becomes the new thesis, and the fourth generation proposes an antithesis. The fifth generation rebels against the fourth generation, and proposes a synthesis. And so on. This is called, in Hegel, “the rational dialectic.” Pure reason, in this sense, is a future reality that is pulling us toward itself through the dialectic like a black hole. The human race is becoming inevitably and unstoppably more reasonable, and it is through reason that the world will be saved, and all individuals will on the last day think the same way and have the same perspective. Then, the noumenal and phenomenal worlds will be identical.

However, we must resist the notion that we are perfectly reasonable today, because to suggest that we are dogmatically correct today is to fall into the trap of believing that no antithesis will come—that our beliefs can never be falsified, which is to fall into the error of the Premoderns, in Hegel’s view. So, Hegel taught, Christianity is the most rational expression of the noumenal realm today, and for that reason ought to be believed, but we must hold in principle that it will be overcome and antithesized in the future, and therefore ought to be held in an open hand.

Hegel thought that the human race was born in a religious state, and was liberated from that state through objective ethical thinking, and will one day be rescued from merely ethical thinking into a bliss of pure aesthetic enjoyment through the rational dialectic. In this way, Hegel saw the world unfolding in three acts as the path every man ought to journey for himself—he is born stupid and religious, and grows into an ethical state, and through reason learns to achieve existential bliss.

Hegel gave birth to two movements—his defenders and detractors. His defenders believed that the world ought to move in a more homogenous direction in which all individuals eventually meld into a single perspective, where everything is the same, and individuality is not important. Obviously, Hegel is in this way at the root of Marxism.

Detracting from Hegel are those who thought individuality was the essence of rationality—to be an individual was the irreducible element of being reasonable, and in that sense Hegel’s detractors conceived Hegel as the opposite of rationality.

This detraction was represented most famously be Søren Kierkegaard, who argued that Hegel had the three acts of the world in exactly the opposite order.  Kierkegaard argued that aesthetic enjoyment is not the sophisticated highest tier of human existence, but is rather the mental state of the infant—drooling, blissful, right according to his own mind. Then, man exits the aesthetic stage of his life and enters the ethical, and achieves the highest tier—the religious mode of existence—which is his authentic encounter with God as an individual, in which he recognizes that God has the right to do whatever he wants with him. It is only in this state of individuality—which Kierkegaard calls “authenticity” that a man can be reasonable, ethical, and properly celebrate true beauty in the world as that to which he is not entitled.

In this existential age, one ethical entailment is that moral principles have been relativized. In the rejection of Kant through Hegelianism, Hume’s dictum “You can’t get from Is to Ought” haunted the world, and the human race pondered the potential consequences of a modernist view of the world that couldn’t justify a universal conception of “the good” as Socrates had defended thousands of years earlier.


Postmodernism frontloads the axiological, not the metaphysical as the premoderns or the epistemological as the moderns. Postmodern was rooted in Hegelian existentialism, but was jolted into existence by the Holocaust. Many philosophers, such as Emanuel Levinas and Martin Buber, saw the Nazi party as representative of the inevitable consequence of the Enlightenment. They philosophized that modernism’s inability to see metaphysical realities allowed the Nazis to dehumanize the Jews, because the Nazis were slaves to a myth of rationality that was in reality a way of masking their attempt to gain political power.

So, philosophy had two options in the 21st century to prevent another Holocaust—go back to Premodernism and give human beings dignity through acknowledging their metaphysical value (such as the soul), or abandon metaphysics entirely and frontload axiology—that is, frontload one’s ethical responsibility to one’s neighbor, and to global justice. Then, epistemology simply becomes a tool in defending and fortifying that pursuit of justice. In this way, postmodernism is always on the hunt for the agenda behind truth claims. Postmodernism sees any claim to “objective truth” as a veiled attempt to gain power over another human being by persuading them to submit to their way of seeing the world.

We must recognize here that postmodernism did not originate the claim that we do not have access to objective truth—that was Kant, who fortified the distinction between the noumenal world and the phenomenal world. All that needed to occur for the relationship between those worlds to be broken is for some event to occur which casts enough suspicion on the transcendental to distrust it. That event was the Holocaust. And once you’re stuck in the phenomenal world with no trustworthy transcendental to mediate the noumenal world to you, you’re stuck in your subjectivity.

In this way, the task of philosophy became the establishment of global justice, not because people were eager to abandon truth, but because through Descartes, Hume, and Kant, people became blind to metaphysics, and therefore blind to the necessary theological foundations which exist at the very bottom of every philosophical question. Postmodernism is not an eager pursuit of relativism, but a desperate scramble to minimize the ethical damages that secularism has wreaked on the world through an unchecked modernism.

Today, we exist not so much in a postmodern age, but in an age of competing modernities. People don’t know how to become enchanted with the metaphysical world again. People are grasping toward something more than materialism, but can’t attain it, because the structure of modernity requires them to begin with epistemology, which dictates a principle of radical doubt which will never allow the justification of metaphysics.

What direction should we go? How can we become enchanted with the world? Should we all become Presocratics again and start from scratch by claiming that “all is fire”? Certainly not. As the Judeo-Christian worldview emphasizes, the only way to begin with metaphysics is not to speculate about the metaphysical world, but to have the metaphysical world reach out to you. Christians have historically called this metaphysical contact “Revelation”—God deigns to reach down into the material world and manifest himself to those who will accept his self-witness.

Much more could be said about the relationship between philosophy and theology, and the complex ways that philosophy has bearings upon our cultural moment, but for the purpose of keeping this summary as short as possible, the doctrine of revelation is as good a place as any to conclude this comprehensive survey of the entire history of philosophy.

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