Organon

The Organon (from the ancient Greek órganon, "instrument") is the name given to a set of six treatises on logic and dialectic attributed to Aristotle. It was not conceived as a single work by its author: the texts were written over a long period and were arranged deliberately, it is thought by Theophrastus and later, around 40 BC, by Andronicus of Rhodes, who gave them a systematic structure. The name "Organon" became established in the Middle Ages, expressing the idea that logic is the necessary instrument for any kind of knowledge.

The six treatises are the Categories, On Interpretation, the Prior Analytics, the Posterior Analytics, the Topics and On Sophistical Refutations. The Categories introduce a classification of what exists into ten kinds: substance, quantity, quality, relation, place, time, position, possession, action and passion. On Interpretation studies the judgement and the proposition, and the relations of opposition between affirmative, negative, universal and particular propositions. The Prior Analytics set out the theory of the syllogism, its figures and moods, and discuss inductive inference. The Posterior Analytics deal with demonstration and scientific knowledge, which rests on premises that are true, primary and better known than the conclusion. The Topics concern dialectical argument, which yields probable rather than certain conclusions, and it is here that the predicables later developed by Porphyry appear. On Sophistical Refutations gathers fallacies and misleading arguments.

Its influence was immense. In late antiquity and the early Middle Ages, only the Categories and On Interpretation, translated by Boethius along with Porphyry's Isagoge, were widely known in the West; the rest arrived in the twelfth century through Latin and Arabic versions. Thinkers in the Islamic and Jewish worlds, such as Avicenna, Averroes and Maimonides, studied the Organon, and the great scholastic philosophers wrote commentaries on it. For centuries it formed the basis of philosophical teaching. With the rise of modern logic in the nineteenth century, Aristotelian logic lost prominence, although it is now recognised that the work of Boole and Frege extends it rather than contradicts it.