Testimony, Luck, and Conversational Implicature

Abstract Speakers convey messages in a variety of ways, including assertion, presupposition, and conversational implicature. Assertion is the paradigm vehicle for acts of testifying. The speaker gives her word to her audience that the presented content is true, allowing them to gain knowledge via a distinctive mechanism: believing on the speaker’s say-so. This is made possible by the conventions and norms that govern the social practice of making assertions, encapsulated in assertion’s being governed by the norm that one must: assert that P only if one knows that P. Do other means of conveying a message also amount to testifying to it? I first examine presupposition, which can be used as a sneaky way to inculcate belief in an audience without it being subject to attention and scrutiny. I then turn to conversational implicature, which I show is an epistemically fragile means of conveying a message, and as such is not apt to be, and is not, governed by a social norm, as the robust communicative means assertion is. We see that only explicit assertion of a conveyed message amounts to testifying to it.