Engaging a listener’s trust imposes moral demands upon a presenter in respect of truthtelling and completeness. An agent lies by an utterance that satisfies what are herein defined as signal and mendacity conditions; an agent deceives when, in satisfaction of those conditions, the agent’s utterances contribute to a false belief or thwart a true one. I advert to how we may fool ourselves in observation and in the perception of our originality. Communication with others depends upon a convention or practice of presumed nonuniversal truthfulness. In support of an asserted duty of nondeceptiveness, I offer a reconciliation of pertinent Kantian passages, a sketch of arguments within utilitarianism, contractarianism, and other views, and an account arguing for application of that duty to assertions, implicatures, omissions, equivocation, prevarication, and sophistry insofar as they affect listeners’ doxastic states. For scholarship, this duty is exceptionless. I describe the kernel of intellectual honesty as a virtuous disposition such that when presented with an incentive to deceive, the agent will not deceive. Intellectual honesty delivers candor when it counts. I contrast this with complementary virtues and the surpassing virtue of ingenuousness. An account is given of the connection between intellectual honesty and an influential physical model of integrity.