Abstract: How are epistemic goods like knowledge, justification, and certainty connected? I argue that these epistemic goods can be understood in terms of one notion: the possibility of error. One knows a true proposition p iff given the way in which one believes that p the possibility of believing falsely is sufficiently slim. One’s belief is justified iff given the way in which one believes the possibility that one ends up knowing is sufficiently high. The degree to which one’s belief is justified is a function of how possible it is that one’s way of believing yields knowledge. Finally, one is epistemically certain that p iff there is no possibility that one ends up ignorant given the way in which one is psychologically certain that p is the case.
This framework places knowledge, justification, and certainty on a continuum and vindicates several independently plausible connections between them, while also giving rise to new interesting results. For instance, the view entails that epistemic certainty entails both knowledge and a maximal degree of justification. It predicts that knowledge doesn’t entail justification, thus supporting the existence of unreasonable knowledge (Lasonen 2010; Williamson 2014). The view entails that the KK-principle is invalid for knowledge, but that a suitably formulated positive introspection principle is valid for certainty. This provides a rationale for an error-theory regarding arguments for the KK-principle; some of those who argue for the KK-principle have mixed up knowledge and certainty. I demonstrate how Dorst’s (2019) argument for the KK-principle can be dismantled by the proposed framework.
After laying out some of the extensional and structural properties of knowledge, justification, and certainty I turn to examine the normative roles of these epistemic goods. I argue that each of these goods can be identified with a central normative notion. Knowledge provides the evaluative standard of success in the epistemic domain. Thus beliefs which fail to amount to knowledge are bad, but we cannot necessarily criticize those who end up ignorant. Justification is the central epistemic norm of belief. By violating a norm one merits personal criticism unless one is excused or exempted from complying with the norm. In the case of violating an epistemic norm this criticism will manifest as a distinctly epistemic response (Kauppinen 2018). Finally, epistemic certainty is the epistemic ideal. Epistemic certainty is epistemic perfection attainable by creatures such as us with respect to particular propositions. While it is interesting in its own right to figure out what the epistemic ideal is because some of us might hope to achieve it in certain domains, an account of the epistemic ideal will also shed light on normative questions regarding ordinary thinkers. How close to the ideal can we reasonably expect others to get informs when beliefs are justified (Pasnau 2013). Our tolerance to the possibility of ignorance depends on our expectations of how close we can get to the ideal.
