What is knowledge? How does it differ from mere belief? Do you need to be able to justify a claim in order to count as knowing it? How can we know that the outer world is real and not a dream?Questions like these are ancient ones, and the branch of philosophy dedicated to answering them - epistemology - has been active for thousands of years. In this thought-provoking Very Short Introduction, Jennifer Nagel considers these classic questions alongside new puzzles arising from recent discoverie...