This document discusses different sources of knowledge and methods of acquiring knowledge. It outlines several ways that humans gain knowledge, including common sense, intuition, beliefs, tradition, personal experience, authority, reason/logic, and scientific methods. The document also summarizes Charles Peirce's four methods of "fixing belief" or determining what is true - tenacity, authority, a priori reasoning, and the scientific method. The scientific method is described as a way to satisfy doubts and reach the same conclusions, where conclusions are determined by external factors instead of human thinking.