Epistemology: The Nature of Knowledge

Introduction

Epistemology, from the Greek episteme (knowledge) and logos (study), is the branch of philosophy concerned with the nature, origin, and limits of human knowledge. While we use the word “know” dozens of times a day—“I know where my keys are,” “I know that 2+2=4,” “I know that my friend is sad”—philosophical inquiry reveals that defining exactly what it means to know something is a complex and daunting task.

This lesson explores the fundamental definition of knowledge that dominated Western philosophy for over two millennia: Knowledge as Justified True Belief (JTB).

The Tripartite Theory of Knowledge (JTB)

Since Plato’s Theaetetus, knowledge has traditionally been defined by three necessary and sufficient conditions. For a subject ( $S$ ) to know a proposition ( $P$ ), the following must hold:

Truth: $P$ must be true. One cannot “know” something that is false. If you claim to know that the Earth is flat, and the Earth is in fact round, you do not have knowledge; you have a mistaken belief.
Belief: $S$ must believe that $P$ . Knowledge requires a mental state of affirmation. You cannot know something if you are completely unaware of it or if you actively disbelieve it.
Justification: $S$ must have good reasons or evidence for believing $P$ . A “lucky guess” that happens to be true does not count as knowledge. If you believe it will rain tomorrow because a magic 8-ball told you so, and it does rain, your belief was true but not justified.

Under this framework, knowledge is the intersection of Truth, Belief, and Justified Reason.

Key Arguments: The Role of Justification

The most debated element of the JTB account is justification. What qualifies as a “good reason”? Epistemologists generally fall into two camps regarding the source of justification:

Internalism: The view that the grounds for justification must be cognitively accessible to the subject. To be justified, I must be able to “reflect” on my reasons.
Externalism: The view that justification can depend on factors outside the subject’s conscious awareness, such as the reliability of the cognitive process (e.g., clear eyesight or a functioning memory) that produced the belief.

Critiques: The Gettier Problem

In 1963, Edmund Gettier published a three-page paper that shattered the long-standing JTB consensus. He provided counterexamples—now known as “Gettier Cases”—where a subject has a justified true belief that intuitively does not seem like knowledge.

Example: The Clock Case Imagine you walk into a room and look at a clock that says it is 12:00 PM. You believe it is 12:00 PM, and your belief is justified because the clock is usually reliable. As it happens, it is 12:00 PM. However, unbeknownst to you, the clock stopped exactly twelve hours ago. You have a belief (It’s 12:00), it’s true (It is 12:00), and it’s justified (You looked at a clock). But do you know it’s 12:00? Most people say “no”—it was just a coincidence.

Gettier’s critique forced philosophers to reconsider whether a fourth condition is needed (e.g., “the belief must not be inferred from a falsehood”) or if the JTB framework must be replaced entirely.

Varieties of Knowledge

It is also important to distinguish between different types of knowledge:

Propositional Knowledge (Knowledge-that): Knowing that a statement is true (e.g., “I know that Paris is in France”). This is the primary focus of epistemology.
Procedural Knowledge (Knowledge-how): Knowing how to perform a task (e.g., “I know how to ride a bicycle”). This often involves “muscle memory” and cannot always be articulated in words.
Acquaintance Knowledge (Knowledge-of): Familiarity with a person, place, or thing (e.g., “I know the city of London”).

Contemporary epistemology has expanded beyond the individual mind to consider Social Epistemology. This sub-field investigates how we acquire knowledge through testimony, the role of experts in society, and the impact of “echo chambers” on our collective understanding of truth. In an era of rampant misinformation (“fake news”), the philosophical study of justification is more critical than ever. We must ask: How do we weigh the testimony of others? When is it rational to defer to scientific authority?

Furthermore, the rise of “Big Data” and algorithmic decision-making has introduced the concept of Epistemic Injustice, where certain groups are unfairly discredited as knowledgeable subjects due to prejudice. Understanding the nature of knowledge is thus not just a theoretical exercise, but a prerequisite for a just and functioning society.