 In this section we will explore how it is that the elimination of possibilities corresponding to information-gain is the starting point for research on logics of knowledge and belief that fall under the heading of epistemic logics. We will begin with classic single-agent epistemic logic, before exploring multi-agent epistemic logics. In both cases, since we will be concentrating on logics of knowledge as opposed to logics of belief, the information-gained will be hard information. 