Epistemology is philosophical study of knowledge, including its nature, origins, and limits. It's also known as the theory of knowledge. Epistemology examines: What knowledge is: What it means to know something, and how to distinguish between knowing and not knowing How knowledge is created: The sources of knowledge, such as perception, inference, and testimony The extent and limits of knowledge: What people can and cannot know, and whether there are things that are unknowable.