Knowledge - a series of brief introductions

What is knowledge? And how does it differ from belief? Do we need to justify a claim for it to be considered knowledge? And how can we be sure that the external world is real and not a dream? These are old and modern questions, contemplated by Jennifer Nagel; the author of this small book, and she tries to answer them, relying on the philosophical study of epistemology, from its earliest questions to our modern era. Nagel's effort revolves around three main pillars: humanity, language, and reason. The author explains how the main historical theories about knowledge were formulated, and also clarifies what contemporary philosophers have developed as new ways to understand knowledge, using ideas from logic, linguistics, and psychology.