  (For a more detailed account see the entry on  Aristotle’s Logic  in this encyclopedia.) Aristotle is the first great logician in the history of logic. His logic was taught by and large without rival from the 4th to the 19th centuries CE.  Aristotle’s logical works were collected and put in a systematic order by later Peripatetics, who entitled them the Organon or ‘tool’, because they considered logic not a part but rather an instrument of philosophy. The Organon contains, in traditional order, the Categories, De Interpretatione, Prior Analytics, Posterior Analytics, Topics and Sophistical Refutations. In addition, Metaphysics Γ is a logical treatise that discusses the principle of non-contradiction, and some further logical insights are found scattered throughout Aristotle’s other works, such as the Poetics, Rhetoric, De Anima, Metaphysics Δ and Θ, and some of the biological works. Some parts of the Categories and Posterior Analytics would today be regarded as metaphysics, epistemology or philosophy of science rather than logic. The traditional arrangement of works in the Organon is neither chronological nor Aristotle’s own. The original chronology cannot be fully recovered since Aristotle seems often to have inserted supplements into earlier writings at a later time. However, by using logical advances as a  criterion, we can conjecture that most of the Topics, Sophistical Refutations, Categories and Metaphysics Γ predate the De Interpretatione, which in turn predates the Prior Analytics and parts of the Posterior Analytics.