Most modern epistemologies violate philosophical conditions of sense, as first formulated by Kant, because they assume a standpoint that transcends knowledge. This investigation works out in detail the sensible, linguistic, and meaning-theoretic foundations of a theory of knowledge that is committed to knowability. This approach succeeds not only in concisely reformulating and solving the problem of the external world but also in providing a fundamental, linguistic interpretation of Kant's Critique of Pure Reason.