This book explores problems of knowledge that arise in everyday life. If you are not an expert, how can you know that another person is an expert? If experts are politically biased should you still trust them? More generally, how should you approach the testimony of other people: treat it all as "innocent until proven guilty," or is that too simple? Does the internet make us better knowers, or is it just a minefield of misinformation? Is it always irrational to believe a conspiracy theory? Suppose someone just as intelligent and well-informed as you are disagrees with you about something, how should that affect your belief? Can we have knowledge of what is right and wrong? HOW DO YOU KNOW? approaches these issues through the lens of social epistemology and via the pre-eminently social genre of philosophical dialogue. Its characters think and speak like real people in the world today, discussing and debating issues that are current, practically relevant, and even controversial -- while equipping readers with tools and concepts to see more clearly for themselves.