Knowledge, concept of

7. Epistemic principles

Epistemic principles describe the normative epistemic status of propositions under varying conditions (see Epistemic logic). It is generally agreed that if a person, S, is justified in believing any proposition, x, then S is not at the same time justified in believing that not-x. Foundationalists and coherentists alike can, and typically do, accept this principle. Other principles are more controversial. They are intuitively plausible but they seem to provide a basis for scepticism and for some deep epistemic puzzles. Here are three of the more interesting principles.

In each principle and with suitable grammatical modifications ‘justified’ could be replaced by other epistemic terms, such as ‘reasonable’, ‘plausible’, ‘evident’, ‘certain’. Furthermore, each principle is designed to capture a basis upon which a positive normative epistemic status of a proposition can be transferred to another proposition. As a corollary, ‘S is justified in believing x’ is not taken to entail ‘S does believe that x, justifiably’. For S may not form the belief because of a failure to see the connection between the propositions. Finally, with regard to CLO-P and ET-P, since a tautology is entailed by every proposition, the entailment must be restricted to some form of relevant entailment and/or the range of propositions must be restricted to contingent ones (see Relevance logic and entailment). Other restrictions are no doubt necessary; but these three seemingly intuitive principles have been challenged at their core.

It is important to see some of the relationships between these principles. CLO-P does not entail CON-P since the CLO-P is about one proposition that S is justified in believing, not sets of propositions. In addition, CLO-P does not entail ET-P because CLO-P does not require that it is the very same evidence, e, that S has for x that justifies y for S. Thus, one can accept CLO-P without accepting either of the other principles.