The Isagoge or "Introduction" to Aristotle's "Categories"

Categories (Aristotle)

The Categories is a text from Aristotle's Organon that enumerates all the possible kinds of thing that can be the subject or the predicate of a proposition...

, written by Porphyry

Porphyry (philosopher)

Porphyry of Tyre , Porphyrios, AD 234–c. 305) was a Neoplatonic philosopher who was born in Tyre. He edited and published the Enneads, the only collection of the work of his teacher Plotinus. He also wrote many works himself on a wide variety of topics...

 in Greek

Ancient Greek

Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...

 and translated into Latin by Boethius, was the standard textbook on logic for at least a millennium after his death. It was composed by Porphyry in Sicily

Sicily

Sicily is a region of Italy, and is the largest island in the Mediterranean Sea. Along with the surrounding minor islands, it constitutes an autonomous region of Italy, the Regione Autonoma Siciliana Sicily has a rich and unique culture, especially with regard to the arts, music, literature,...

 during the years 268-270, and sent to Chrysaorium, according to all the ancient commentators Ammonius

Ammonius Saccas

Ammonius Saccas was a Greek philosopher from Alexandria who was often referred to as one of the founders of Neoplatonism. He is mainly known as the teacher of Plotinus, whom he taught for eleven years from 232 to 243. He was undoubtably the biggest influence on Plotinus in his development of...

, Elias, and David. The work includes the highly influential hierarchical classification of genera

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 and species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 from substance in general down to individuals, known as the Tree of Porphyry, and an introduction which mentions the problem of universals.

Boethius' translation of the work, in Latin, became a standard medieval textbook in European schools and universities, setting the stage for medieval philosophical-theological developments of logic and the problem of universals. Many writers, such as Boethius himself, Averroes

Averroes

' , better known just as Ibn Rushd , and in European literature as Averroes , was a Muslim polymath; a master of Aristotelian philosophy, Islamic philosophy, Islamic theology, Maliki law and jurisprudence, logic, psychology, politics, Arabic music theory, and the sciences of medicine, astronomy,...

, Abelard, Scotus, wrote commentaries on the book. Other writers such as William of Ockham

William of Ockham

William of Ockham was an English Franciscan friar and scholastic philosopher, who is believed to have been born in Ockham, a small village in Surrey. He is considered to be one of the major figures of medieval thought and was at the centre of the major intellectual and political controversies of...

 incorporated them into their textbooks

Sum of Logic

The Summa Logicae is a textbook on logic by William of Ockham. It was written around 1323.Systematically, it resembles other works of medieval logic, organised under the basic headings of the Aristotelian Predicables, Categories, terms, propositions, and syllogisms...

 on logic.

Versions

The earliest Latin translation, which is now no longer extant, was made by Marius Victorinus in the fourth century. Boethius heavily relied upon it in his own translation. The earliest known Syriac translation was made in the seventh century by Athanasius of Balad

Athanasius of Balad

Athanasius of Balad AD was a medieval scholar and the patriarch of Antioch, Syria. A Christian monophysite, he devoted himself to Greek philosophy. He produced commentaries and translations of Greek texts into Syriac.- Quotes :...

. An early Armenian translation of the work also exists.
The Introduction was translated into Arabic by Ibn al-Muqaffa‘ from a Syriac version. With the Arabicized name Isāghūjī it long remained the standard introductory logic text in the Muslim world and influenced the study of theology, philosophy, grammar, and jurisprudence. Besides the adaptations and epitomes of this work, many independent works on logic by Muslim philosophers have been entitled Isāghūjī. Porphyry's discussion of accident sparked a long-running debate on the application of accident and essence.

The Predicables

The predicables

Predicables

Predicables is, in scholastic logic, a term applied to a classification of the possible relations in which a predicate may stand to its subject. It is not to be confused with 'praedicamenta', the schoolmen's term for Aristotle's ten Categories...

 (Lat. praedicabilis, that which may be stated or affirmed, sometimes called quinque voces or five words) is, in scholastic logic

Term logic

In philosophy, term logic, also known as traditional logic or aristotelian logic, is a loose name for the way of doing logic that began with Aristotle and that was dominant until the advent of modern predicate logic in the late nineteenth century...

, a term applied to a classification

Categorization

Categorization is the process in which ideas and objects are recognized, differentiated and understood. Categorization implies that objects are grouped into categories, usually for some specific purpose. Ideally, a category illuminates a relationship between the subjects and objects of knowledge...

 of the possible relations in which a predicate may stand to its subject

Subject (philosophy)

In philosophy, a subject is a being that has subjective experiences, subjective consciousness or a relationship with another entity . A subject is an observer and an object is a thing observed...

. The list given by the schoolmen and generally adopted by modern logicians is based on the original fivefold classification given by Aristotle

Aristotle

Aristotle was a Greek philosopher and polymath, a student of Plato and teacher of Alexander the Great. His writings cover many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, linguistics, politics, government, ethics, biology, and zoology...

 (Topics

Topics (Aristotle)

The Topics is the name given to one of Aristotle's six works on logic collectively known as the Organon. The other five are:*Categories*De Interpretatione*Prior Analytics*Posterior Analytics*On Sophistical Refutations...

, a iv. 101 b 17-25): definition

Definition

A definition is a passage that explains the meaning of a term , or a type of thing. The term to be defined is the definiendum. A term may have many different senses or meanings...

 (horos), genus (genos), differentia (diaphora), property (idion), accident

Accident (philosophy)

Accident, as used in philosophy, is an attribute which may or may not belong to a subject, without affecting its essence. The word "accident" has been employed throughout the history of philosophy with several distinct meanings....

 (sumbebekos).

The scholastic classification, obtained from Boëthius's version of the Isagoge, modified Aristotle's by substituting species (eidos) for definition.

The Porphyrian tree

In medieval textbooks, the all-important Arbor porphyriana

Arbor porphyriana

An arbor porphyriana or Porphyrian tree, created by Porphyry, is a hierarchical ontology, construction in logic consisting of three rows or columns of words; the middlemost whereof contains the series of genus and species, and bears some analogy to the trunk...

("Porphyrian Tree") illustrates his logical classification of substance. To this day, taxonomy benefits from concepts in Porphyry's Tree, in classifying living organisms: see cladistics

Cladistics

Cladistics is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants . For example, birds, dinosaurs, crocodiles, and all descendants of their most recent common ancestor form a clade...

.

The problem of universals

The work is celebrated for prompting the medieval debate over the status of universals. Porphyry writes

For the moment, I shall naturally decline to say, concerning genera and species, whether they subsist, whether they are bare, pure isolated conceptions, whether, if subsistent, they are corporeal or incorporeal, or whether they are separated from or in sensible objects, and other related matters. This sort of problem is of the very deepest, and requires more extensive investigation.

Though he did not mention the problem further, his formulation constitutes the most influential part of his work, since it was these questions that formed the basis of medieval debates about the status of universals. Do universals exist in the mind, or in reality? If in reality, are they physical things, or not? If physical, do they have a separate existence from physical bodies, or are they part of them?