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How does epistemology study the sources and limits of human knowledge?

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Four colored straws in a glass of water appear bent at the water's surface, visually demonstrating the refraction of light. — Epistemology The refraction (bending) of light as it passes from air into water causes an optical illusion: straws in the glass of water appear broken or bent at the water's surface.

Epistemology is the branch of philosophy dedicated to studying the nature, origin, and limits of human knowledge. It investigates how we acquire knowledge, what constitutes a valid claim to know, and the boundaries of what can be known.12

Sources of Knowledge

Philosophers have long debated the primary sources of knowledge, most notably through the historical tension between empiricism and rationalism:

Empiricism: Asserts that all concepts and justifiable beliefs originate in or are tested through experience.
Rationalism: Argues that reason or the intellect is the fundamental source of knowledge, capable of grasping truths beyond the reach of sense perception.3

Limits and Challenges

Epistemology explores the limits of knowledge by examining the conditions required for a belief to count as "knowledge." Historically, this has been defined as justified true belief, though this definition faces challenges such as the Gettier problem, which questions whether justification is always sufficient for knowledge.4

Furthermore, skepticism serves as a critical limit by challenging the possibility of knowledge itself. Skeptics argue that because it is often logically possible to be mistaken—such as the hypothetical scenario of being a "brain in a vat"—we cannot claim absolute certainty regarding the external world.2