This chapter investigates the conflict between thought and speech that is inherent in lying. This is the conflict of saying what you think is false. The chapter shows how stubbornly saying what you think is false resists analysis. In traditional analyses of lying, saying what you think is false is analyzed in terms of saying something and believing that it is false. But standard cases of unconscious or divided belief challenge these analyses. Classic puzzles about belief from Gottlob Frege and (...) Saul Kripke show that suggested amendments involving assent instead of belief do not fare better. I argue that attempts to save these analyses by appeal to guises or Fregean modes of presentation will also run into trouble. I then consider alternative approaches to untruthfulness that focus on (a) expectations for one’s act of saying/asserting and (b) the intentions involved in one’s act of saying/asserting. Here I introduce two new kinds of case, which I call “truth serum” and “liar serum” cases. Consideration of these cases reveals structural problems with intention- and expectation-based approaches as well. Taken together, the string of cases presented suggests that saying what you think is false, or being untruthful, is no less difficult and interesting a subject for analysis than lying itself. Tackling the question of what it is to say what you think is false illuminates ways in which the study of lying is intertwined with fundamental issues in the nature of intentional action. (shrink)