Peter Helias (c. 1100 – after 1166) was a medieval priest and philosopher. Born in Poitiers

Poitiers

Poitiers is a city on the Clain river in west central France. It is a commune and the capital of the Vienne department and of the Poitou-Charentes region. The centre is picturesque and its streets are interesting for predominant remains of historical architecture, especially from the Romanesque...

, he became a pupil of Thierry of Chartres

Thierry of Chartres

Thierry of Chartres or Theodoric the Breton was a twelfth-century philosopher working at Chartres and Paris, France....

 at Paris

Paris

Paris is the capital and largest city in France, situated on the river Seine, in northern France, at the heart of the Île-de-France region...

 in the 1130s, also teaching grammar

Grammar

In linguistics, grammar is the set of structural rules that govern the composition of clauses, phrases, and words in any given natural language. The term refers also to the study of such rules, and this field includes morphology, syntax, and phonology, often complemented by phonetics, semantics,...

 and rhetoric

Rhetoric

Rhetoric is the art of discourse, an art that aims to improve the facility of speakers or writers who attempt to inform, persuade, or motivate particular audiences in specific situations. As a subject of formal study and a productive civic practice, rhetoric has played a central role in the Western...

 in his school. Around 1155 he returned to Poitiers where he later died.

Other influences beside Thierry include William of Conches

William of Conches

William of Conches was a French scholastic philosopher who sought to expand the bounds of Christian humanism by studying secular works of the classics and fostering empirical science. He was a prominent member of the School of Chartres...

. He contributed to the theory of substance, and through Thierry, is meant to have been influenced particularly by Boethius

Anicius Manlius Severinus Boethius

Anicius Manlius Severinus Boëthius, commonly called Boethius was a philosopher of the early 6th century. He was born in Rome to an ancient and important family which included emperors Petronius Maximus and Olybrius and many consuls. His father, Flavius Manlius Boethius, was consul in 487 after...

.

In linguistics

Linguistics

Linguistics is the scientific study of human language. Linguistics can be broadly broken into three categories or subfields of study: language form, language meaning, and language in context....

, he is regarded as having contributed ideas key to the development of grammatical categories such as parts of speech

Lexical category

In grammar, a part of speech is a linguistic category of words , which is generally defined by the syntactic or morphological behaviour of the lexical item in question. Common linguistic categories include noun and verb, among others...

.

Works

• a commentary on Cicero
  Cicero
  Marcus Tullius Cicero , was a Roman philosopher, statesman, lawyer, political theorist, and Roman constitutionalist. He came from a wealthy municipal family of the equestrian order, and is widely considered one of Rome's greatest orators and prose stylists.He introduced the Romans to the chief...
  
  's De inventione
  De Inventione
  The De Inventione is a handbook for orators that M. Tullius Cicero composed when he was still a young man. Quintillian tells us that Cicero considered the work rendered obsolete by his later writings. Originally four books in all, only two have survived into modern times.-External links:* by C.D....
  
  
• c. 1150: Summa super Priscianum, an updated textbook on Priscian
  Priscian
  Priscianus Caesariensis , commonly known as Priscian, was a Latin grammarian. He wrote the Institutiones grammaticae on the subject...
  
  's Institutiones grammaticae, edited by Leo A. Reilly, Toronto 1993