  The dictionary definition of deception is as follows: “To cause to believe what is false” (OED 1989). There are several problems with this definition, however (Barnes 1997; Mahon 2007; Carson 2010). The principal problem is that it is too broad in scope. On this definition, mere appearances can deceive, such as when a white object looks red in a certain light (Faulkner, 2013). Furthermore, it is possible for people to inadvertently deceive others. If Steffi believes that there is a talk on David Lewis and the Christians on Friday, and she tells Paul that “There is a talk on Lewis and the Christians on Friday,” and as a result Paul believes that there is a talk on C. S. Lewis and the Christians on Friday, then Steffi has deceived Paul. Also, it is possible for people to mistakenly deceive other people. If Steffi mistakenly believes that there is not a philosophy talk on Friday, and she tells Paul that there is not a philosophy talk on Friday, and he believes her, then then Steffi has deceived Paul.