Epistemology: The Philosophy of Knowledge

How can we know that our beliefs are justified? In this article, we explore this difficult question as we learn about epistemology, the philosophy of knowledge.

Nov 1, 2021By Casey Scott, MA Philosophy, GDipEd English and Humanities, BA(Hons) Professional & Creative Writing

Epistemology philosophy knowledge


Epistemology is the philosophy of knowledge, or the study of knowledge itself, what it is and how it is possible. Knowledge was first defined by Plato as justified true belief. After Plato, Ancient Greek skeptics proposed that there is no surefire way to justify a belief. We will take a glance at one of the more difficult questions within philosophy, which is: how can I know that my belief is justified? To begin, let’s take a look at justified belief, its problems, and then explore some of the solutions philosophy provides.


Epistemology: The Munchhausen Trilemma

Hans Albert, photograph by Frank Luwe, via the Hans Albert Institute


The term ‘Munchhausen Trilemma’ was coined by German philosopher Hans Albert and refers to the threefold problem in epistemology of justified belief: all beliefs are either justified by other beliefs, based on foundational facts, or are self-supported.


In the first case being true, our beliefs cannot be justified since that would lead to an infinite regress. In the second instance, we must rely on our faith that some beliefs are true. In the third instance, our beliefs cannot be justified because they would be examples of circular reasoning. To explain this further, let’s take a look at an example in popular culture, as it appears in The Big Bang Theory.


The Big Bang Theory, screenshot courtesy of Symmetry Magazine


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In an episode of The Big Bang Theory titled The Bad Fish Paradigm, Sheldon uses the Munchhausen Trilemma to explain his reason for moving out of his apartment to his housemate, Leonard.


Sheldon Cooper: Leonard, I’m moving out.

Leonard Hofstadter: What do you mean, you’re moving out? Why?

Sheldon Cooper: There doesn’t have to be a reason?

Leonard Hofstadter: Yeah, there kinda does.

Sheldon Cooper: Not necessarily. This is a classic example of Munchhausen’s Trilemma: either the reason is predicated on a series of sub-reasons, leading to an infinite regression; or it tracks back to arbitrary axiomatic statements; or it’s ultimately circular: i.e., I’m moving out because I’m moving out.


Sheldon shows that there are three ways to justify his reason for moving out and that each method fails to properly justify his reason for moving out. If he uses other reasons to support his reason for moving out his argument either turns into an infinite regress or it becomes circular. Most of us have some experience with this problem, as demonstrated by children who repeatedly ask ‘why?’ something is the case or why they have been asked to do something. In most cases, there comes a point where the carer gives up in exhaustion and says “because I told you so.” This is epistemology in practice.


Epistemology and the Philosophy of Agrippa the Sceptic 

Engraving of Sextus Empiricus by Officina Wetsteniana, 1692, via The British Museum, London


Of course, Hans Albert was not the first philosopher to identify this problem within epistemology. One of the earliest accounts of this problem is described by the philosopher Sextus Empiricus (1st or 2nd c. CE), first credited to the Greek philosopher Agrippa the Sceptic.


According to Agrippa, here are the five principles for why we cannot have belief with any certainty:


  1. Dissent, or disagreement. This is the uncertainty caused by people disagreeing on something.
  2. Argument ad infinitum. All beliefs are based on reasons, which are themselves based on reasons, ad infinitum.
  3. Relation. Different perspectives and contexts seem to change the meaning of things so that it is difficult to define what that something is.
  4. Assumption. Most (maybe all) truth claims and arguments include unsupported assumptions.
  5. Circularity. We often try to justify our beliefs by using our belief as a reason for the belief. For example, I like bananas because they are good. However, I obviously would not like bananas if they were not good. So this is the same as saying I like bananas because I like bananas. This is known as circular reasoning.


The five modes show us that it can be difficult to justify a belief. So how can we know that our beliefs are justified? For the rest of this article, we will look at potential solutions to each of the three main epistemological concerns that we saw in Munchhausen’s Trilemma: infinite regress, dogmatism and circularity. They are infinitism, foundationalism and coherentism.


Infinitism and Epistemology

Galatea of the Spheres by Salvador Dali, 1952, via Dalí Theatre-Museum


Infinitism accepts the first horn of the Munchhausen Trilemma, the infinite regress. Infinitism is the view that our reasons are supported by other reasons, which are supported by other reasons. The controversial aspect of infinitism is that it argues that this chain of reasons goes on indefinitely. In other words reason A is supported by reason B, which is supported by reason C which is supported by reason D… etc. ad infinitum.


So why would anyone choose infinitism as their model of epistemic justification? After all, doesn’t it suggest that all our beliefs are ultimately unfounded? Perhaps. However, proponents of infinitism argue that infinitism encounters fewer problems than foundationalism or coherentism, making it more parsimonious.



Portion of marble fluted column, Classical Greek, ca. 350 BC, via the British Museum, London


Foundationalism takes on the second horn of the trilemma: that some beliefs are unquestionably foundational and do not require further justification. Foundationalists call these types of beliefs basic beliefs. For example, not many people would dispute that things in the world exist, and that their existence gives us a reason to believe that they exist. The fact that my cat exists is a reason itself to believe that it exists. Basic beliefs require no further explanation to be justified.


Of course, foundationalism is not without its criticisms. The most common argument against foundationalism is that it seems to require reasons for the very belief that some beliefs require no further explanation. If so, that would require further explanation and therefore further supporting reasons. If such criticisms hold weight, then foundationalism seems to end up at the first horn – an infinite regress – or the third horn – circularity.



Vir Heroicus Sublimis by Barnett Newman, 1951, via MOMA


Coherentism challenges the third horn of the trilemma – circularity. The most basic understanding of coherentism is that beliefs are justified when they cohere with sets of reasons that are relevant to and logically harmonious with the belief. So if belief A is coherent with a set of beliefs B, it can be said to be justified. At a minimum, it can be said to make sense.


Contemporary philosopher Jamie Watson suggests that coherentism faces the problem of contradictory sets of beliefs that cohere to themselves, therefore making seemingly incompatible beliefs equally justified. The ancient Greeks had a word that describes this phenomenon where contradictory beliefs appear equally justified, they called it equipollence. This raises questions about whether any belief is more justified than another.


As you can see, philosophers have long since tackled questions about our beliefs and how we can know they are true or justified. We have looked at three well-known solutions to epistemological scepticism, although there are many more. To conclude, let’s take a look at a few honourable mentions.



Photograph of Bertrand Russell, courtesy of the British Broadcasting Corporation, 1960, via Encyclopedia Britannica


Fallibilism is the view in epistemology that our beliefs are liable to err. In other words, with any held belief we can also assume that we may be shown to be wrong. When British philosopher Bertrand Russell was asked by an interviewer for the New York Post whether he would die for his philosophy, Russell answered with:


“Of course not… after all, I may be wrong.


This, in a nutshell, is fallibilism. Science works in accordance with fallibilism since it does not claim to know ultimate truths; rather, we can only know what is evident to us at a certain time. Science is constantly changing in light of new evidence.



Evidence of a mermaid? – Merman, taxidermy/sculpture, 18th century, via The British Museum


The idea behind this epistemology is quite straightforward: for any belief to be justified it must be supported by evidence. If you cannot provide evidence then your belief is unsupported.


Of course, this sounds simple enough, although for evidentialism to be persuasive it requires an account of what counts as evidence. For different people of different cultures, the word ‘evidence’ has many meanings. Even within science, there is debate about what counts as evidence.



Karl Popper, photograph, via Encyclopedia Britannica


Following on from evidentialism, we have falsificationism. Philosopher Karl Popper describes falsificationism as a way in epistemology of distinguishing scientific hypotheses from pseudoscience, a method which can also be used to determine whether a belief is justified.


If an idea is worthy of investigation, such as the belief that all grass is green, it ought to be falsifiable — it ought to have the possibility of being shown untrue.


In light of falsificationism, some beliefs can never be justified. There are types of ideas that cannot be shown to be true or false with clear evidence. To give an example, belief in ghosts is not justified because no evidence could be provided to show that ghosts do not exist (they’re supposed to be invisible after all).


On the other hand, one could falsify the belief that all grass is green by finding some grass that is not green. But if no evidence can be provided that shows there are types of grass of other colours, my belief that grass is green remains justified.


Epistemological nihilism

The Taste of Emptiness by Jean Dubuffet, 1959, via MOMA


We will finish with the most sceptical epistemology, epistemological nihilism. It is even hard to say if epistemological nihilism is an epistemology or not. Ultimately, epistemological nihilism is the view that knowledge either does not exist or that true knowledge is impossible, perhaps for the reasons discussed in this article.


Of course, epistemological nihilism begs the question. If one claims that they know nothing, the question arises as to how one can know that they know nothing. In there, somewhere, there seems to be knowledge of some kind.

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By Casey ScottMA Philosophy, GDipEd English and Humanities, BA(Hons) Professional & Creative WritingCasey teaches philosophy and culture studies at a leading Australian university. His postgraduate research examined the metaphysics of biological concepts. He is a qualified English teacher with a degree in professional and creative writing and is about to begin his third degree in zoology and animal sciences.