This paper argues that two claims usually included in any minimally detailed presentation of the epistemic closure principle are inconsistent. The first claim states that the closure principle explains how we extend our knowledge through deduction, while the second claim states that the closure principle is different from another epistemic principle, namely, the principle of transmission. The attempt to offer a correct diagnosis of reasonings such as the one involved in Dretske's zebra case is an instance of a discussion in which the distinction plays a role. To defend my position, I first introduce the distinction between closure and transmission following the standard presentation. Second, I introduce the main motivations behind the principles; in particular, I establish that the main motivation behind closure consists in explaining the phenomenon that we extend our knowledge through deductive reasoning. Third, based on the identification of a restriction on any plausible formulation of closure capable of explaining this phenomenon, I cast doubt on the distinction between this principle and transmission. I conclude that any formulation of the epistemic principle of closure which satisfies its main motivation collapses into the epistemic principle of transmission. [ABSTRACT FROM AUTHOR]