Aristotle, in Posterior Analytics B.10, separates three stages in scientific enquiry: (1) knowledge of the signification of the relevant terms, (2) knowledge of the existence of the kind, and (3) knowledge of the essence of the kind. One can, in all relevant cases, achieve the first stage of enquiry without (as yet) achieving the second or third stages. So, knowledge of the signification of the relevant terms does not essentially involve knowledge of the existence of the kind in question.
Keywords: Aristotle, essence, existence, Posterior Analytics, scientific discovery, signification