The Organon (Ὄργανον, meaning "instrument, tool, organ") is the standard collection of Aristotle's six works on logical analysis and dialectic. The name Organon was given by Aristotle's followers, the Peripatetics, who maintained against the Stoics that Logic was "an instrument" of Philosophy.
The term "organon" is neither found in Aristotle, nor does it occur in the writings of Plato. The book, according to M. Barthélemy St. Hilaire, was not called "Organon" before the 15th century, and the treatises were collected into one volume, as is supposed, about the time of Andronicus of Rhodes; and it was translated into Latin by Boethius about the 6th century.
The six works of Organon are as follows:
The order of the works is not chronological (which is now hard to determine) but was deliberately chosen by Theophrastus to constitute a well-structured system. Indeed, parts of them seem to be a scheme of a lecture on logic. The arrangement of the works was made by Andronicus of Rhodes around 40 BC.
Aristotle's Metaphysics has some points of overlap with the works making up the Organon but is not traditionally considered part of it; additionally, there are works on logic attributed, with varying degrees of plausibility, to Aristotle that were not known to the Peripatetics.
The Categories (Latin: Categoriae) introduces Aristotle's 10-fold classification of that which exists: substance, quantity, quality, relation, place, time, situation, condition, action, and passion.
On Interpretation (Latin: De Interpretatione) introduces Aristotle's conception of proposition and judgement, and the various relations between affirmative, negative, universal, and particular propositions. Aristotle discusses the square of opposition or square of Apuleius in Chapter 7 and its appendix, Chapter 8. Chapter 9 deals with the problem of future contingents.
The Prior Analytics (Latin: Analytica Priora) introduces his syllogistic method (see term logic), argues for its correctness, and discusses inductive inference.