What is Epistemology in Philosophy?

Epistemology is the branch of philosophy that deals questions relevant to knowledge and belief, and the related topics of justification, truth, and types of certainty. There are a number of questions pertinent to epistemology. For instance, what is knowledge, and how is it acquired? What makes belief justified? And what are the limits of belief? Much of the contemporary debate among epistemologists focuses on several areas: (i) the relationship between truth, belief, and justification; (ii) skepticism; (iii) the scope of knowledge and justified belief; and (iv) the criteria for knowledge and justification (3).

Why is epistemology important? It is important because philosophy, as Aristotle (384–322 BCE) himself once saw, begins with wonder. Many of us want to understand the world and universe in which we live, and that no doubt includes engaging some of those perennial philosophical questions. Part of learning about the world is our ability to construct theories that, proponents hope, make sense of reality. Philosophers, no doubt, are particularly captivated by understanding the world which would itself explain why epistemology proves to be such a lively branch of philosophy (4).

As mentioned, epistemology deals with knowledge. Knowledge, simply defined, is the understanding of particular aspects of reality that are derived from information gained through the process of reason (5). Traditionally, for epistemologists, a proposition is required to meet three necessary and sufficient conditions to be accepted as a justified true belief: truth, belief, and justification. Firstly, for a proposition to count as knowledge, it must be true. Second, a belief is an expression of faith or trust in something (entity, person etc.). And third, justification concerns whether or not a belief is justified, and whether we should/should not/may believe a proposition. A justified true belief then is one that meets these three conditions sufficient for knowledge (6).

Now, there are number of schools of thought that deal with the topic of justification, namely evidentialism, reliabilism, and infallibilism. An evidentialist, for example, believes that a belief is justified on the basis of evidence (7). In other words, a person, S, is justified in believing a proposition, P, if and only if S’s evidence for P supports believing P. A reliabilist believes either that justification is not necessary for knowledge provided it is a reliably-produced true belief, or that justification is required but any reliable cognitive process (vision, for example) is sufficient justification (8). Thirdly, an advocate of infallibilism will argue that knowledge is a true belief that cannot be rationally doubted. On this view, a belief must not only be true and justified, but that the justification of the belief must necessitate its truth, so that the justification for the belief must be infallible.

According to philosophers there are two types of provisional knowledge: a priori and a posteriori (9). A priori knowledge refers to knowledge that is justified independent of experience, for example, knowledge that does not depend on experiential evidence or warrant. Alternatively, a posteriori knowledge is knowledge justified by way of experience, and thus depends on experiential evidence or warrant. Moreover, philosophers have held to a number of theories of knowledge acquisition such as rationalism (knowledge is acquired by a priori processes or is innate (in the form of concepts) or intuitive), empiricism (knowledge that is acquired via the five senses), representationalism (the view that the world we see as conscious beings is not the real world itself, as opposed to a miniature copy of that world in an internal representation), and constructivism (the view that all knowledge is constructed from human perception and social experience).

Though we will examine religious epistemology, and the relationship between epistemology, spirituality, and theology in some more detail later, I have found being aware of epistemology to be helpful. This is because it has assisted me, as well as many others, in not only identifying self-defeating propositions but also answering them. This is particularly valuable today because many hold to views, knowingly or unknowingly, that are obviously self-defeating. For example, one might say that “we can’t know anything for certain,” which is obviously self-defeating because it makes at least one claim to knowledge. Another might say that “objective truth doesn’t exist.” That, however, is at least one claim to objective truth (one might retort, “Is that objectively true?”). Or, as some advocates of contemporary forms of spirituality who hope to be open and tolerant might say, “All truth is relative.” Again, one might respond that that is an objective truth claim which means that not all truth is relative. Further, many of the disagreements between, say, naturalists and theists are epistemological in nature. For example, the existence of God, the supernatural, and the reality of miracles are pertinent questions that theists and atheists, both of whom could be evidentialists, would disagree on (10).

Epistemology has also been helpful in that it promotes what one might deem a healthy skepticism. I use the term “healthy” deliberately because not all forms of skepticism are reasonable (see hyper-skepticism, for example). A healthy skepticism tells us that we shouldn’t just believe anything someone tells us (as in the self-defeating claims mentioned above), or believe everything we hear or read. Rather, a reasonable skepticism says that we need to have reasons and evidence for what we believe; in other words, the belief has to be justified.


3. Borchert, D (ed.). 1967. “Epistemology,” in the Encyclopedia of Philosophy.

4. Stroll, A., & Martinich, A. Epistemology. Available.

5. Goldman, A., & Beddor, B. 2008. Reliabilist Epistemology. Available.

6. Steup, M. 2005. Epistemology. Available.

7. Steup, M. 2005. Ibid; Mittag, D. Evidentialism. Available.

8. Goldman, A., & Beddor, B. 2008. Ibid.

9. New World Encyclopedia. A priori and a posteriori. Available.

10. McCormick, M. Atheism. Available.




  1. I would disagree with the claim that “A justified true belief then is one that meets these three conditions sufficient for knowledge.”

    Gettier, and Plato before him, showed that justified true belief cannot be sufficient for knowledge.

      • This is from my post on epistemology:

        “He asks us to consider the following case. Smith and Jones both apply to a job. Smith was told by the company that Jones will win the job. Smith knows that there are ten coins in Jones’ pocket and combines that fact with what the company told him. Thus, Smith develops the belief that the person who will get the job has ten coins in his pocket. However, Smith is unaware of the fact that he also has ten coins in his pocket. And surprisingly, it is Smith who ends up getting the job. It seems then that Smith was right that the person who will get the job has ten coins in his pocket. He was justified in making that belief (based on the company’s testimony), and smith believed that this is the case. He therefore satisfies all three conditions for knowledge: justification, truth, belief. Yet, it seems odd to say that Smith knew he would get the job, since he thought that Jones would get the job.
These Gettier cases can be generalized and crafted in many different ways. They do, I think, show clearly that knowledge requires more than justified true belief.”

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