The document discusses the challenges of determining what is true in an age where most of our knowledge comes from sources other than direct experience. It notes that political campaigns have long been dishonest, and examines how we evaluate the reliability of testimony from sources like journalists, experts, and social media. It emphasizes the importance of considering the independence of sources, evaluating each link in the "testimonial chain", and getting as close as possible to the original event or documentation when assessing the veracity of claims.