Chapter 8 opens by asking readers to reflect on the attributes of someone who they find trustworthy and believable. It then describes three attributes that Aristotle described for credible people: practical intelligence, virtuous character, and goodwill. Modern research on people’s perceptions of scientific sources finds similar attributes: expertise, integrity, and benevolence. The chapter reviews ways that science communicators can show these attributes. For example, we need to understand the phenomenon we’re sharing; we need to be honest, which can include saying "I don’t know" when applicable; and we need to be respectful. Being clear is a sign of respect for our conversational partners, as is sincere listening. This chapter returns to a comparison of the deficit model and funds of knowledge approaches before discussing ways to handle opinions that contradict the scientific consensus or that are in some way offensive. The Worked Example concerns stereotypes. This chapter’s Closing Worksheet asks readers to identify three things about their demonstrations that they are confident about and three things that they do not know related to their demonstrations.

Chapter 9 opens with an overly detailed recipe for lentil soup that readers remove steps from. Many people new to public engagement express concern about "dumbing down" their science, for example by leaving out critical nuance. The chapter discusses examples like the recipe exercise, in which some details are omitted without compromising truth. In these examples, fewer details effectively enhance clarity. Three suggestions for balancing the Maxim of Quality (tell the truth) with the Maxim of Quantity (say as much as you need but not more) are: to distinguish phenomena from explanations, to distinguish classics from hot news, and to emphasize process. Readers are encouraged to take the long view, thinking of every science conversation as contributing a little to someone’s learning. If nothing else, a demonstration that generates people’s interest and excitement is likely to inspire them to learn more later. This chapter’s Closing Worksheet asks readers to go through the explanations in their demonstrations and to keep cutting out 10 percent until they are left with a reasonable description of the phenomenon and a one-sentence take-home message.