Truth, like knowledge, is surprisingly difficult to define. We seem to rely on it almost every moment of every day and it's very "close" to us. Yet it's difficult to define because as soon as you think you have it pinned down, some case or counterexample immediately shows deficiencies. Ironically, every definition of truth that philosophers have developed falls prey to the question, "Is it true?"

Simply, we can define truth as: a statement about the way the world actually is. We'll look at various theories below that philosophers have considered but that's an adequate rough-and-ready definition to get us started. Coming up with a definition of truth falls under the discipline of epistemology or the study of knowledge though some philosophers categorize it as a study in metaphysics--the study of what is real.

In this essay, we'll look at some reasons why defining truth can be challenging. Truth seems like something we naturally comprehend and while intuition can help us a great deal in understanding what it is, surface definitions present us with unique problems and I’ll illustrate why. I'll then lay out some terms and concepts that will help us get a better handle on understanding what truth is. Next, we'll look at three main views of truth. The coherence theory describes truth in terms of interconnected belief. A belief is true if it is consistent with other beliefs we have. The correspondence theory describes truth in terms of a relation concepts or propositions have to the actual world. Finally postmodernism lays out a view of truth in terms of individual perspectives and community agreement. While this essay does not focus on practical issues like why a view of truth is important, I'll say a few words about that idea at the end and provide more resources for further reading.

Elusive Definition of Truth

I stated above that defining truth can be challenging. Let’s briefly look at why this is so by way of a seemingly simple example. Suppose you examine an apple and determine that it’s red, sweet, smooth and crunchy. You might claim this is what the apple is. Put another way, you've made truth claims about the apple and seemingly made statements about real properties of the apple. But immediate problems arise. Let's suppose your friend is color blind (this is unknown to you or her) and when she looks at the apple, she says that the apple is a dull greenish color. She also makes a truth claim about the color of the apple but it's different than your truth claim. What color is the apple?

Well, you might respond, that's an easy problem to solve. It's actually red because we've stipulated that your friend has an anomaly in her truth-gathering equipment (vision) and even though we may not know she has it, the fact that she does means her view of reality is incorrect. But now let’s suppose everyone is color blind and we all see "red" apples as green? We can make this objection even stronger by asking how we know that we all aren't in fact color blind in a way we don't understand and apples really aren't red after all. No one has access to the “real” color of the apple. Again, the response might be that that this is a knowledge problem, not a truth problem. The apple really is red but we all believe it’s green. But notice that the truth of the apple’s color has little role to play in what we believe. No one knows what the truth is and so it plays no role in our epistemology.

The challenge is that our view of truth is very closely tied to our perspective on what is true. This means that in the end, we may be able to come up with a reasonable definition of truth, but if we decide that no one can get to what is true (that is, know truth), what good is the definition? Even more problematic is that our perspective will even influence our ability to come up with a definition! These are no small concerns and we'll explore some responses below.

Preliminaries: Truth and Meaning

Before we get to definitions of truth, we need to define some terms used in those definitions which will make things a little easier to digest. Epistemologists (people who study truth, belief and knowledge) use the following concepts as the framework for their study of truth.

Propositions. A common technical definition of a proposition (credited to Peter van Inwagen) is "a non-linguistic bearer of truth value." A proposition is a representation of the world or a way the world could possibly be and propositions are either true or false. Propositions are different than sentences. Sentences are symbolic, linguistic representations of propositions. Okay, that's all very technical. What does it mean?

Let's take the sentence, "The moon has craters." This is an English sentence that supposedly states some fact about the world or reality (and specifically about the moon). Because it’s in English, we say it's "linguistic" or language-based. If we're going to get philosophical about it, we could describe its properties as having four words and 17 letters, it's in the English language written in 11 point font and it's black. I could write the same sentence like this:

The moon has craters .

This sentence has different properties from the first one above. This one still has the same number of words and letters and it's in English. But it is in 18 point font and is written in blue. Now let's take this sentence, "La luna tiene cráteres." This sentence has four words but 19 letters. It's written in 11 point font and is black but it's Spanish. What do all three sentences have in common? Well, they all express the same idea or meaning and we could say the same "truth." We could express the same idea in Swahili, semaphore, Morse code, or any other symbolic system that conveys meaning.

Notice that the symbols themselves are neither true nor false. The meaning the sentences represent is either true or false. Sentences are symbolic representations of something else—propositions. The common property true of all sentences that express the same truth is what philosophers call the propositional content of the sentences or "the proposition." Now we can better understand the idea behind "non-linguistic bearer of truth value." Propositions are non-linguistic because they aren't written or spoken in a language. They bear truth because they are the things that are true or false. This is what allows them to be expressed or "exemplified" in a variety of different symbolic systems like language-based sentences. When it comes to understanding truth, many philosophers believe propositions are at the center.

Belief. Beliefs are things (at least) people have. They don't exist outside the mind. Some philosophers say beliefs are "dispositional." That is, they incline a person to behave in a way as if the thing they believe is true. So a belief, simply, is a proposition that a person accepts as representing the way the world actually is. Beliefs can be about false propositions and thus be "wrong" because the person accepts them as true. This is a critical distinction. While a proposition has to be true or false, beliefs can be about true or false propositions even though a person always accepts them as being true.

Some philosophers attempt to define truth "mind-independently." That means, they want to come up with a definition that doesn't depend on whether humans can actually believe or know what is true. Truth is viewed as independent of our minds and they seek a definition of it that captures this. Other philosophers have developed theories that keep people at the center. That is, truth and belief are considered together and are inseparable. I will try to make the relevance of the "epistemic" vs. "independent" views of truth relevant below.

Knowledge. Knowledge is belief in a true proposition that a person is justified in holding as true. The conditions under which a person is justified is complicated and there are many theories about when the conditions are met. Theories of knowledge attempt to describe when a person is in a "right" cognitive relationship with true propositions. I describe some theories of knowledge and some of the challenges in understanding when a person knows in an article for Philosophy News called "What is Knowledge?"

Common Definitions of Truth

The Coherence View of Truth

The main idea behind this view is that a belief is true if it "coheres" or is consistent with other things a person believes. For example, a fact a person believes, say "grass is green" is true if that belief is consistent with other things the person believes like the definition of green and whether grass exists and the like. It also depends on the interpretation of the main terms in those other beliefs. Suppose you’ve always lived in a region covered with snow and never saw grass or formed beliefs about this strange plant life. The claim "grass is green" would not cohere with other beliefs because you have no beliefs that include the concept "grass." The claim, "grass is green" would be nonsense because it contains a nonsensical term "grass." That is, you never formed a belief about grass so there’s nothing for this new belief to cohere with.

As you can see from the above description, coherence theories typically are described in terms of beliefs. This puts coherence theories in the "epistemic" view of truth camp noted above. This is because, coherence theorists claim, we can only ground a given belief on other things we believe. We cannot "stand outside" our own belief system to compare our beliefs with the actual world. If I believe Booth shot Lincoln, I can only determine if that belief is true based on other things I believe like "Wikipedia provides accurate information" or "My professor knows history and communicates it well" or "Uncle John sure was a scoundrel".

These are other beliefs and serve as a basis for my original belief. Thus truth is essentially epistemic since any other model requires a type of access to the "real world" we simply can't have. As philosopher Donald Davidson describes the situation, "If coherence is a test of truth, there is a direct connection with epistemology, for we have reason to believe many of our beliefs cohere with many others, and in that case we have reason to believe many of our beliefs are true." (Davidson, 2000)

The Correspondence Theory of Truth

Arguably the more widely-held view of truth (stemming from a broader rationalist tradition in philosophy), philosophers who argue for the correspondence theory hold that there is a world external to our beliefs that is somehow accessible to the human mind. More specifically, correspondence theorists hold that there are a set of "truth-bearing" representations (or propositions) about the world that align to or correspond with reality or states of affairs in the world. A state of affairs just is a particular way the world or reality is. When a proposition aligns to the world, the proposition is said to be true. Truth, on this view, is that correspondence relation.

Take this proposition: "The Seattle Seahawks won Super Bowl 48 in 2014." The proposition is true if in fact the Seahawks did win super Bowl 48 in 2014 (they did) and false if they didn't.

Notice that on this view, propositions about reality are different from beliefs we may have of reality. We believe propositions--I believe that the moon has craters. What follows the "that" is meant to signify the proposition that a person believes. So truth on this view is when the proposition matches reality.

The correspondence theory only lays out the condition for truth in terms of propositions and the way the world actually is. This definition does not involve beliefs that people have. Propositions are true or false regardless of whether anyone believes them. Just think of a proposition as a way the world possibly could be: "The Seahawks won Super Bowl 48" or "The Seahawks lost Super Bowl 48" -- both propositions possibly are true. True propositions are those that correspond to what actually happened.

You'll notice that this definition does not include a belief component. That is, unlike the coherence theory, the correspondence theory describes truth in terms that are independent of beliefs humans may have. This has the distinct advantage of separating truth from the messy business of belief and knowledge but may warrant complaints of being impractical.

Postmodernism and Truth

Postmodern thought covers a wide theoretical area but informs modern epistemology particularly when it comes to truth. Postmodern theories of truth are difficult to articulate in strict terms because postmodern theorists tend to eschew hard and fast definitions. But we can provide some insight here. Put in simple terms, postmodernists describe truth not as a relationship outside of the human mind that we can align belief to but as a product of belief. We never access reality because we can never get outside our own beliefs to do so. Our beliefs function as filters that keep reality (if such a thing exists) beyond us. Since we can never access reality, it does no good to describe knowledge or truth in terms of reality because there's nothing we can actually say about it that's meaningful. Truth then is constructed by what we perceive and ultimately believe.

Immanuel Kant

I'm inclined to earmark the foundation of postmodern thought with the work of Immanuel Kant, specifically with his work The Critique of Pure Reason. In my view, Kant was at the gateway of postmodern thought. He wasn't a postmodernist himself but provided the framework for what later developed.

Kant makes a foundational distinction between the "objects" of subjective experience and the "objects" of "reality." He labels the former phenomena and that latter noumena. The noumena for Kant are things in themselves (ding an sich). These exist outside of and separate from the mind. This is what we might call "reality" or actual states of affairs similar to what we saw in the correspondence theory above. But for Kant, the noumena are entirely unknowable in and of themselves. However, the noumena give rise to the phenomena or are the occasion by which we come to know the phenomena.

The phenomena make up the world we know, the world "for us" (für uns). This is the world of rocks, trees, books, tables, and any other objects we access through the five senses. This is the world of our experience. This world, however, does not exist apart from our experience. It is essentially experiential. Kant expressed this idea as follows: the world as we know it is "phenomenally real but transcendentally ideal." That is, things that we believe exist in the world are a "real" part of our subjective experience but they do not exist apart from that subjective experience and don't transcend the ideas we have. The noumena are "transcendentally real" or they exist in and of themselves but are never experienced directly or even indirectly.

For example, suppose you look at an apple. You see a specific shape and color. You can pick it up and feel its weight and bite into it and taste that it’s sort of sweet and maybe a bit sour. These all are your experiences of the apple. Kant suggests that these experiences do not tell us much about the ‘real’ apple. After all, how could we know that our experience is of the real apple? Perhaps another person would see a slightly different color when she looks at the apple. Or if you just had something very sweet, the apple will taste more sour but if you had something very sour, the apple might taste more sweet. So what is the ‘real’ flavor of the apple? Kant (and postmodernists in general) would say that this isn’t a good question since we can never get beyond our subjective experience to answer it. Rather, we can say that the phenomena—the colors, shapes, and taste—that we experience is for us and very real for us. But we can’t get beyond (transcend) that subjective experience. Instead, we should describe the apple in just those terms. I can say, “The apple tastes sweet to me." But I can’t really say, “The apple is sweet.” since it’s not possible to actually know anything beyond subjective experience.

The noumena are given form and shape by what Kant described as categories of the mind and this 'ordering' gives rise to phenomenal objects. This is where it relates to truth: phenomenal objects are not analogues, copies, representations or any such thing of the noumena. The noumena gives rise to the phenomena but in no way resembles them. Scholars have spent countless hours trying to understand Kant on this point since it seems like the mind interacts with the noumena in some way. But Kant does seem to be clear that the mind never experiences the noumena directly and the phenomena in no way represents the noumena.

We can now see the beginnings of postmodern thought. If we understand the noumena as “reality” and the phenomena as the world we experience, we can see that we never get past our experience to reality itself. It's not like a photograph which represents a person and by seeing the photograph we can have some understanding of what the "real person" actually looks like. Rather (to use an admittedly clumsy example) it's like being in love. We can readily have the experience and we know the brain is involved but we have no idea how it works. By experiencing the euphoria of being in love, we learn nothing about how the brain works.

On this view then, what is truth? Abstractly we might say truth is found in the noumena since that's reality. But postmodernists have taken Kant's idea further and argued that since we can't say anything about the noumena, why bother with it at all? Kant didn’t provided a good reason to believe the noumena exists but seems to have asserted its existence because, after all, something was needed to give rise to the phenomena. Postmodernists just get rid of this extra baggage and focus solely on what we experience.

Perspective and Truth

Further, everyone's experience of the world is a bit different--we all have different life experiences, background beliefs, personalities and dispositions, and even genetics that shape our view of the world. This makes it impossible, say the postmodernists to declare an "absolute truth" about much of anything since our view of the world is a product of our individual perspective. Some say that our worldview makes up a set of lenses or a veil through which we interpret everything and we can't remove those lenses. Interpretation and perspective are key ideas in postmodern thought and are contrasted with "simple seeing" or a purely objective view of reality--something postmodernists reject as impossible.

We only have interconnected beliefs and for each individual, that's what truth is. We can see some similarities here to the coherence theory of truth with its web of interconnected and mutually supported beliefs. But where the coherence theory holds that coherence among beliefs gives us reason to hold that what we believe corresponds to some external reality, postmodernists reject that. In postmodernism there is nothing for our beliefs to correspond to or if there is, our beliefs never get beyond the limits of our minds to enable us to make any claims about that reality.

Community Agreement

Postmodernism differs from radical subjectivism (truth is centered only in what an individual experiences) by allowing that there might be "community agreement" for some truth claims. The idea is that two or more people may be able to agree on a particular truth claim and form a shared agreement that a given proposition is true. To be clear, it's not true because they agree it maps or corresponds to reality. But since the group all agree that a given proposition or argument works in some practical way, or has explanatory power (seems to explain some particular thing), or has strong intuitive force for them, they can use this shared agreement to form a knowledge community.

When you think about it, this is how things tend to work. A scientist discovers something she takes to be true and writes a paper explaining why she thinks it's true. Other scientists read her paper, run their own experiments and either validate her claims or are unable to invalidate her claims. These scientists then declare the theory "valid" or "significant" or give it some other stamp of approval. In most cases, this does not mean the theory is immune from falsification or to being disproved--it's not absolute. It just means that the majority of the scientific community that have studied the theory agree that it’s true given what they currently understand. This shared agreement creates a communal "truth" for those scientists. This is what led Richard Rorty to state the oft-quoted phrase, "Truth is what my colleagues will let me get away with."

Truth in Real Life

Philosophers are supposed to love wisdom and wisdom is more oriented towards the practical than the theoretical. This article has been largely about a theoretical view of truth so how do we apply it? Most people don't spend a whole lot of time thinking about what truth is but tend to get by in the world without that understanding. That's probably because the world seems to impose itself on us rather than being subject to some theory we might come up with about how it has to operate. We all need food, water and shelter, meaning, friendship, and some purpose that compels us to get out of bed in the morning. This is a kind of practical truth that is not subject to the fluidity of philosophical theory.

Even so, we all contend with truth claims on a daily basis. We have to make decisions about what matters. Maybe you're deeply concerned about politics and what politicians are claiming or what policy should be supported or overturned. Perhaps you care about which athlete should be traded or whether you should eat meat or support the goods produced by a large corporation. You may want to know if God exists and if so, which one. You probably care what your friends or loved ones are saying and whether you can count on them or invest in their relationship. In each of these cases, you will apply a theory of truth whether you realize it or not and so a little reflection on what you think about truth will be important.

Your view of truth will impact how you show up at work and impacts the decisions you make about how to raise your children or deal with a conflict. For example, suppose you're faced with a complex question at work about something you're responsible for. You need to decide whether to ship a product or do more testing. If you're a postmodernist, your worldview may cause you to be more tentative about the conclusions you're drawing about the product's readiness because you understand that your interpretation of the facts you have about the product may be clouded by your own background beliefs. Because of this, you may seek more input or seek more consensus before you move forward. You may find yourself silently scoffing at your boss who makes absolute decisions about the "right" way to move forward because you believe there is no "right" way to do much of anything. There's just each person's interpretation of what is right and whoever has the loudest voice or exerts the most force wins.

An engineer may disagree here. She may argue, as an example, that there is a "right" way to build an airplane and a lot of wrong ways and years of aviation history documents both. Here is an instance where the world imposes itself on us: airplanes built with wings and that follow specific rules of aerodynamics fly and machines that don't follow those "laws" don't. Further most of us would rather fly in airplanes built by engineers that have more of a correspondence view of truth. We want to believe that the engineers that built the plane we're in understand aerodynamics and built a plane that corresponds with the propositions that make up the laws of aerodynamics.

Your view of truth matters. You may be a correspondence theorist when it comes to airplanes but a postmodernist when it comes to ethics or politics. But why hold different views of truth for different aspects of your life? This is where a theory comes in. As you reflect on the problems posed by airplanes and ethics, the readiness of your product to be delivered to consumers and the readiness of your child to be loosed upon the world, about what makes you happy and about your responsibility to your fellow man, you will develop a theory of truth that will help you navigate these situations with more clarity and consistency.

Related Articles and Resources

What is Knowledge? Truth is about what is factual whether anyone believes it. Knowledge is about connecting our beliefs with what is true. In this article, we explore this challenging but critical subject, including the impact of postmodernism on knowledge, and it’s the perfect follow up to this article on truth.

What is Skepticism? What do we do if we’re not sure our beliefs align with what is true? In between truth and knowledge is a middle way and this article on skepticism talks about the value of doubt. In a day where falsehoods, fake news, and half-truths seem to be the norm, perhaps taking a more skeptical stance can help us get closer to the truth. Check out this article by Dr. Joseph Shieber to learn more.

What is Logic? Logic is the discipline that helps us connect ideas in the right way so we can determine what is true and what isn’t. In this article, Dr. Paul Herrick walks us through the basics of logical theory and shows shows how logic can help us connect our beliefs to what is true.

Short Little Lessons in Logic. If you want to learn the fundamentals of formal logic, this course will enable you to study at your own pace in bite-sized chunks for free! The course covers the basics of logical theory, how to construct and analyze arguments, the difference between deductive and inductive arguments and much more. The course includes quizzes so you can check your knowledge, videos to help you learn and some interactive exercises to reinforce your learning along the way.

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