Categories (Kategoriai)

Aristotle claims that primary substances, individual things like a particular person or tree, are the basic subjects of reality, while secondary substances (species and genera), qualities, quantities and the rest are either predicated of them or exist in them. This sets aside the Platonic assumption that universal Forms are the most real entities. Everything other than primary substance depends on it: if individual substances did not exist, nothing else could. The treatise is brief and schematic, so it offers a framework rather than a full defense, which later works such as the Metaphysics develop and complicate.

Aristotle distinguishes what is said of a subject, as 'man' is said of Socrates, from what is present in a subject, as a particular shade of white is present in a body. Combining the two yields four kinds of entity: universal substances, individual substances, universal accidents, and individual accidents. The scheme lets him say what makes substances independent without making universals independent. Interpreters, including G. E. L. Owen and Michael Frede, have debated whether individual accidents, such as this particular whiteness, really belong to the framework, a question with consequences for how the whole ontology is read.

This is one of the oldest disputes about the work. Aristotle introduces the categories through the kinds of things that are said without combination, which suggests a linguistic starting point, yet the argument concerns the kinds of beings the words signify. Émile Benveniste argued that the categories merely reflect the grammar of Greek, a claim that Jules Vuillemin and others have criticized as overly reductive. The more common scholarly view is that the treatise sits between language and ontology, classifying what is said in order to articulate what there is.

The work was traditionally placed first in the Organon, the collection of Aristotle's logical treatises assembled by later editors, which is why it served for centuries as the opening of logical study. Its authenticity and unity have nonetheless been questioned: some ancient and modern scholars doubted that all of it, especially the final sections, derives from Aristotle in its present form. Ancient commentators such as Porphyry and Simplicius treated it as foundational, and Porphyry's Isagoge became a standard introduction to it. Most modern scholars accept it as Aristotelian while acknowledging uncertainty about its date and compilation.

Late antique and medieval writers treated it as the basis of logic and read it through Porphyry's Isagoge, with Boethius transmitting the Latin tradition. This produced a debate on universals that shaped medieval philosophy. A common misreading treats the ten categories as a fixed taxonomy of everything, or as Aristotle's complete metaphysics. It is a compact preliminary account, and Aristotle himself varies the list in other works. Kant's own table of categories, derived differently, is also frequently confused with Aristotle's, though the two projects differ in aim and method.

The work survives in Greek and is brief but dense. J. L. Ackrill's translation and notes in the Clarendon Aristotle series is a standard choice for students and is also reprinted in the revised Oxford Translation edited by Jonathan Barnes. Richard Sorabji's collection of ancient commentators in translation shows how the text was read for centuries. Readers should compare how translators render key terms such as ousia, which appears as 'substance' or 'being', and note how choices about the final sections affect interpretation.