Modistae

The Modistae (Latin for Modists), also known as the speculative grammarians, were the members of a school of grammarian philosophy known as Modism or speculative grammar, active in northern France, Germany, England, and Denmark in the 13th and 14th centuries. Their influence was felt much less in the southern part of Europe, where the somewhat opposing tradition of the so-called "pedagogical grammar" never lost its preponderance. 
History.
William of Conches, Peter Helias, and Ralph of Beauvais, also referred to as speculative grammarians predate the Modist movement proper.
The Modist philosophy was first developed by Martin of Dacia (died 1304) and his colleagues in the mid-13th century, though it would rise to prominence only after its systematization by Thomas of Erfurt decades later, in his treatise "De modis significandi seu grammatica speculativa", probably written in the first decade of the 14th century. Until the early twentieth-century this work was assumed to have been authored by John Duns Scotus. Widely reproduced and commented upon in the Middle Ages, it remains the most complete textbook of Modist speculative grammar. The mistaken authorship arose out of the natural affinity of Erfurt's speculative grammar with Scotus's metaphysics.
Theory of modes.
The philosophy of the Modistae, as indicated by their name, was based on a theory of 'modes' of meaning in language which was tripartite: modes of being ("modi essendi"), modes of understanding ("modi intelligendi"), and modes of signifying ("modi significandi"). To the Modistae, the various parts of speech were viewed as representing reality in terms of these modes. The "modi essendi" are objectively existent qualities in an object of understanding, the "modi intelligendi" the understanding's means of representing the "modi essendi", and the "modi significandi" grammar's means of representing the "modi intelligendi" in language. This corresponds to Aristotle's tripartite semantic theory of "words" representing "concepts" which represent "objects".
Opposing nominalism, they assumed that the analysis of the grammar of ordinary language was the key to metaphysics. For the Modistae, grammatical forms, the "modi significandi" of verbs, nouns, and adjectives, comprise the deep ontological structure of language, which objectively reflects reality. Their work predicted the concept of universal grammar, suggesting that universal grammatical rules may be extracted from all living languages. Roger Bacon may have given the movement inspiration with his observation that all languages are built upon a common grammar, a shared foundation of ontologically anchored linguistic structures. He argued grammar is substantially the same in all languages, even though it may undergo accidental variations between languages.
Legacy.
There are parallels between speculative grammar and phenomenology, a fact that was picked up early on by Martin Heidegger, who wrote his first book, "Die Kategorien- und Bedeutungslehre des Duns Scotus" ("Duns Scotus's Doctrine of Categories and Meaning", 1916), on Thomas of Erfurt's treatise (at that time still mistakenly attributed to Duns Scotus).