 Like knowledge, certainty is an epistemic property of beliefs. (In a derivative way, certainty is also an epistemic property of subjects: S is certain that p just in case S’s belief that p is certain.) Although some philosophers have thought that there is no difference between knowledge and certainty, it has become increasingly common to distinguish them. On this conception, then, certainty is either the highest form of knowledge or is the only epistemic property superior to knowledge. One of the primary motivations for allowing kinds of knowledge less than certainty is the widespread sense that skeptical arguments are successful in showing that we rarely or never have beliefs that are certain (see Unger 1975 for this kind of skeptical argument) but do not succeed in showing that our beliefs are altogether without epistemic worth (see, for example, Lehrer 1974, Williams 1999, and Feldman 2003; see Fumerton 1995 for an argument that skepticism undermines every epistemic status a belief might have; and see Klein 1981 for the argument that knowledge requires certainty, which we are capable of having).