This book is about the epistemological views and arguments of the early Stoics. It discusses such questions as: How is knowledge possible, and what is it? How do we perceive things and acquire notions of them? Should we rely on arguments? How do we come to make so many mistakes? The author tries to give a comprehensive and conservative account of Stoic epistemology as a whole as it was developed by Chrysippus. He emphasizes how the epistemological views of the Stoics are interrelated among themselves and with views from Stoic physics and logic. There are a number of Stoic views and arguments that we will never know about. But there are passages on Stoic epistemology in Sextus Empiricus, Galen, Plutarch, Cicero, and a few others authors. The book is like a big jigsaw puzzle of these scattered pieces of evidence.