Introduction to Epistemology

Epistemology is the study of knowledge—especially the question of what it means to truly know something, and why humans need a framework for getting there. The lecture opens by tying the field to Aristotle’s claim that people naturally desire to know, then asks what “knowing” amounts to in practice. That focus matters because it distinguishes reliable understanding from mere thinking, and it explains why questions about knowledge aren’t optional once doubt about perception and reasoning enters the picture.

The term “epistemology” comes from Greek roots meaning knowledge (epistēmē) plus the doctrine or study of (—logy), so it is essentially the theory of knowledge. Epistemology targets core problems such as the nature of knowledge, what blocks people from attaining it, what can be known, and how knowledge differs from opinion or belief. In that sense, having an “epistemology” means holding a view about how knowledge works—what counts as it, how it is obtained, and what makes it trustworthy.

Traditionally, knowledge acquisition is split into two broad routes. Empiricism treats knowledge as coming through the senses and experience: examining a plant, for instance, yields information about its shape, size, smell, texture, and whether it produces flowers or fruit. But the lecture stresses that senses can mislead—people once believed the Earth was flat—and that even modern thinking raises concerns about how bodies and sensory equipment shape what reality seems like. A bat’s perception, for example, is likely unlike a human’s, suggesting that sensory interpretation may be filtered by evolved capacities.

Rationalism offers a different path: knowledge through reasoning. Yet the lecture notes that epistemology often narrows its attention to propositional knowledge, or knowledge of facts—claims that can be true or false, such as “a giraffe has four legs” or “3 × 30 equals 90.” This is contrasted with practical knowledge, or know-how, like knowing how to drive or play baseball. Practical skill is often implicit and unconscious; people don’t consciously “learn” how to step down stairs each time. Martin Heidegger is singled out as treating practical knowledge as more fundamental than propositional knowledge, though even that focus can be framed as seeking propositional facts about how practical knowledge works.

To clarify what propositional knowledge requires, the lecture turns to Nicholas Rescher’s account: knowing a fact is not an activity or performance (“I am knowing…”), but a condition of being in a certain relation to information. That leads to the classic definition of propositional knowledge as justified true belief. Belief alone isn’t enough; the believer must have solid grounds, and must be aware of those grounds. Guesses, conjectures, and opinions that may happen to be correct still fail as knowledge if the person lacks awareness of the reasons the proposition is true.

Finally, the lecture asks why a theory of knowledge is needed at all. If people simply accept what senses deliver or what reasoning produces, epistemology becomes unnecessary. But once doubt arises—whether mental representations match the world—knowledge becomes a problem. The lecture links that problem to fear: fear that senses are too feeble, memory fades, authority and convention blind, and even God or demons may deceive. Lorraine Daston and Peter Galison’s work on objectivity is used to frame epistemology as an attempt to calm that fear by clearing a path toward knowledge, removing sources of error and imperfection that derail human inquiry.