In Posterior Analytics 2.19, Aristotle argues that we cannot have innate knowledge of first principles because if we did we would have the most precise items of knowledge without noticing, which is impossible. To understand Aristotle’s argument we need to understand why he thinks we cannot possess these items of knowledge without noticing. In this paper, I present three different answers to this question and three different readings of his argument corresponding to them. The first two readings focus on the fact that we do not use the knowledge we allegedly possess innately. However, I argue that these readings fail to produce convincing arguments. I then offer a third reading, which focuses on the fact that we do not notice the knowledge we allegedly possess innately when we use it for the first time (i. e., on Plato’s account, when we recollect). I argue that this reading produces a more convincing argument than either of the first two.