Suppose, with Boghossian, that we distinguish epistemic rules and principles. Both are conditionals, but rules have imperatival consequents whereas principles are true or false. To each rule, there corresponds a principle: if the rule says “In C, believe p,” the principle can say either “In C, it is obligatory to believe p” or “In C, it is permissible to believe p.”
Let’s simplify a bit a say that a cognitive system operates in accord with a rule when the imperatival consequent is fulfilled and the antecedent describes the causal/explanatory factors that prompted (in the near enough past) the belief formation in question. We’ll have to say something at some point about deviant causation, but I’ll ignore that for now. Let’s then say, also simplifying, that the good rules are ones that, by operating in accord with them, a person can arrive at a doxastically justified belief. Not that this result is always achieved, but that it can be achieved, i.e., the rule specifies in its antecedent a possible basis for a doxastically justified belief.
Given this stagesetting, it is pretty obvious that the epistemic principles that correspond to the rules that we operate in accord with will be mostly false.
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