 The interplay between knowledge and belief is an important topic in epistemology. Historically, one of the most important proposals is Plato’s characterization of knowledge as  justified true belief,  which has been one of the motivations used in the development of  justification logic.  However, can knowledge be truly defined as justified true belief? The  examples  provided (among others) in Gettier (1963) seem to go against this idea. Gettier describes situations in which an agent believes a given \(\varphi\) and has a justification for it; moreover, \(\varphi\) is indeed the case. Nevertheless, the justification is not an appropriate one: \(\varphi\) happens to be the case because of some other lucky unrelated circumstances. This has lead to proposals that focus on the requirement of a correct justification (the no false lemma: Clark 1963; Armstrong 1973; Shope 1983). Some others have used a stronger indefeasibility requirement, stating that knowledge is justified true belief that cannot be defeated by true information, i.e., there is no true proposition \(\psi\) such that, if the agent were to learn that \(\psi\) was the case, would lead her to give up her belief, or to be no longer justified in holding it (Klein 1971; Lehrer &amp; Paxson 1969; Swain 1974). The aforementioned topological modal approach of Baltag, Bezhanishvili, et al. (2016) relates this idea with other epistemic concepts, and a deeper discussion on what it means to know something can be found in  the analysis of knowledge  by Ichikawa and Steup (2018).