A Defense of Temperate Epistemic Transparency

Epistemic transparency tells us that, if an agent S knows a given proposition p, then S knows that she knows that p. This idea is usually encoded in the socalled KK principle of epistemic logic. The paper develops an argument in favor of a moderate version of KK, which I dub quasi-transparency, as a normative rather than a descriptive principle. In the second Section I put forward the suggestion that epistemic transparency is not a demand of ideal rationality, but of ideal epistemic responsibility, and hence that ideally responsible agents verify transparency principles of some sort; I also contend that their satisfaction should not be tied to an internalist epistemology. The central argument in favor of transparency is then addressed in Sections 3 to 8, through the development of a formal system. I show that, in a well-behaved formal setting, a moderate version of transparency is imposed upon us as a result of a number of independent decisions on the structure of higherorder probabilities, as long as we request that our probability and knowledge attributions cohere with each other. Thus I give a rationale to build a model for a hierarchy of languages with different levels of knowledge and probability operators; we obtain an analogous to KK for successive knowledge operators without actually demanding transitivity. The formal argument reinforces the philosophical intuition that epistemic transparency is an important desideratum we should not be too ready to dismiss.