 Russell’s type theory can be regarded as a solution to Russell’s paradox, since type theory demonstrates how to “repair” set theory such that the paradox disappears. Similarly, Tarski’s hierarchy can be regarded as a solution to the liar paradox. It is the same stratification idea that underlies both of Russell’s and Tarski’s solutions. The point to note is that Russell’s paradox and the liar paradox depend crucially on circular notions (self-membership and self-reference). By making a stratification in which an object may only contain or refer to objects at lower levels, circularity disappears. In the case of the epistemic paradoxes, a similar stratification could be obtained by making an explicit distinction between first-order knowledge (knowledge about the external world), second-order knowledge (knowledge about first-order knowledge), third-order knowledge (knowledge about second-order knowledge), and so on. This stratification actually comes for free in the semantic treatment of knowledge, where knowledge is formalised as a modal operator.