 There has also been some discussion of the concept of knowledge in terms of both reliability and fallibility. Let us begin with the former. Succinctly put, reliabilism holds that a belief is knowledge if it is true and if it was produced, or is sustained, by a reliable process that yields mostly true beliefs. Reliabilist theories of knowledge require a reliable mechanism for belief formation, but do not require that the epistemic agent be aware or have evidence of the mechanism’s reliability. For this reason, reliabilism is a form of externalism. Juan Comesaña (on whom see the previous section) has proposed an original theory of epistemic justification that combines elements of both reliabilism and evidentialism—which represent two competing approaches in contemporary analytic epistemology. This theory, which he calls “evidentialist reliabilism”, is intended to incorporate the best aspects of both positions while avoiding the most serious problems they face (Comesaña 2010). Comesaña has also argued that reliabilism is able to successfully deal with the so-called “generality problem” (Comesaña 2006b), and that the epistemological problems stemming from lotteries either are not peculiar to reliabilism or can be solved by appealing to a probabilistic account of reliability (Comesaña 2009b). He has as well referred to reliability in his discussion of “safety”. Several epistemologists (such as Ernest Sosa, Timothy Williamson, and Duncan Pritchard) have defended the view that safety is a necessary condition for knowledge. Roughly put, what that condition says is that S knows that p if and only if S would believe that p only if p were true. On the basis of a counterexample, Comesaña (2005) has argued that safety, as this notion has been defined by Sosa, is not actually a necessary condition for knowledge. The reason is that, whereas reliability is plausibly a necessary condition for knowledge, reliable reliability is not, and whereas knowledge is compatible with unreliably reliable beliefs, safety is not. Hence, one can have “unsafe” knowledge. Comesaña’s more recent work in collaboration with Matthew McGrath and Stewart Cohen has focused on the part played by false beliefs in epistemology. He has argued that false propositions can be part of one’s evidence or can be reasons to do something (Comesaña &amp; McGrath 2014, 2016) and, against Williamson, that one can have rational or justified false beliefs (Cohen &amp; Comesaña 2013a, 2013b, forthcoming).