Lying and certainty

In the philosophical literature on the definition of lying, the analysis is generally restricted to cases of flat-out belief. This chapter considers lies involving partial beliefs (beliefs ranging from mere uncertainty to absolute certainty). The first section analyses graded-belief lies: lies uttered while holding a graded belief in the falsity of the assertion. A revised insincerity condition is introduced to deal with these cases, requiring that the liar believes the assertion to be more likely to be false than true. The second section analyses assertions that express graded beliefs, exploring how epistemic modals affect the insincerity conditions of a given utterance. The last section considers the case of lies that attack certainty (knowledge lies), understood as attempts to alter the hearer’s graded beliefs.