 The second book of the Posterior Analytics discusses how to achieve this goal of scientific knowledge, one central concern being how knowledge of essences, expressed in definitions, is related to explanations expressed in the form of causal demonstrations. Plato had formulated a famous paradox of inquiry in his dialogue Meno: either you know the object of your inquiry, in which case inquiry is unnecessary; or you don’t know the object of your inquiry, in which case inquiry is impossible (Meno 80d5-e5). Aristotle reminds us of this paradox in the first chapter of the Posterior Analytics, but his full solution only emerges in book II. There, he argues that perceptual experience gives us a grasp of the target of inquiry that, though it does not count as scientific knowledge, does serve to direct further inquiry. He begins the discussion by presenting us with a claim about how objects of inquiry are linked to objects of scientific knowledge.