Latinitas was spoken as well as written, and it was the language taught in schools. Prescriptive rules therefore applied to it, and where a special subject was concerned, such as poetry or rhetoric, additional rules applied. Now that the spoken Latinitas has become extinct (in favor of various other registers later in date) the rules of the, for the most part, polished (politus) texts may give these the appearance of an artificial language, but Latinitas was a form of sermo, or spoken language, and as such retains spontaneity. No texts by Classical Latin authors are noted for the type of rigidity evidenced by stylized art, except possibly the repetitious abbreviations and stock phrases of inscriptions.
Good Latin in philology is "classical" Latin literature. The term refers to the canonicity of works of literature written in Latin in the late Roman Republic and the early to middle Roman Empire: "that is to say, that of belonging to an exclusive group of authors (or works) that were considered to be emblematic of a certain genre." The term classicus (masculine plural classici) was devised by the Romans themselves to translate Greek ἐγκριθέντες (enkrithentes), "select", referring to authors who wrote in Greek that were considered model. Before then, classis, in addition to being a naval fleet, was a social class in one of the diachronic divisions of Roman society according to property ownership by the Roman constitution. The word is a transliteration of Greek κλῆσις (klēsis) "calling", used to rank army draftees by property from first to fifth class.
Classicus is anything primae classis, "first class", such as the authors of the polished works of Latinitas, or sermo urbanus. It had nuances of the certified and the authentic: testis classicus, "reliable witness." It was in this sense that Marcus Cornelius Fronto (an African-Roman lawyer and language teacher) in the 2nd century AD used scriptores classici, "first-class" or "reliable authors" whose works could be relied upon as model of good Latin. This is the first known reference, possibly innovated at this time, to classical applied to authors by virtue of the authentic language of their works.
In imitation of the Greek grammarians, the Roman ones, such as Quintilian, drew up lists termed indices or ordines on the model of the Greek lists, termed pinakes, considered classical: the recepti scriptores, "select writers." Aulus Gellius includes many authors, such as Plautus, who are currently considered writers of Old Latin and not strictly in the period of classical Latin. The classical Romans distinguished Old Latin as prisca Latinitas and not sermo vulgaris. Each author (and work) in the Roman lists was considered equivalent to one in the Greek; for example Ennius was the Latin Homer, the Aeneid was a new Iliad, and so on. The lists of classical authors were as far as the Roman grammarians went in developing a philology. The topic remained at that point while interest in the classici scriptores declined in the medieval period as the best Latin yielded to medieval Latin, somewhat less than the best by classical standards.
The Renaissance brought a revival of interest in restoring as much of Roman culture as could be restored and with it the return of the concept of classic, "the best." Thomas Sébillet in 1548 (Art Poétique) referred to "les bons et classiques poètes françois", meaning Jean de Meun and Alain Chartier, which was the first modern application of the word. According to Merriam Webster's Collegiate Dictionary, the term classical, from classicus, entered modern English in 1599, some 50 years after its re-introduction on the continent. Governor William Bradford in 1648 referred to synods of a separatist church as "classical meetings" in his Dialogue, a report of a meeting between New-England-born "young men" and "ancient men" from Holland and England. In 1715 Laurence Echard's Classical Geographical Dictionary was published. In 1736 Robert Ainsworth's Thesaurus Linguae Latinae Compendarius turned English words and expressions into "proper and classical Latin." In 1768 David Ruhnken (Critical History of the Greek Orators) recast the mold of the view of the classical by applying the word canon to the pinakes of orators, after the Biblical canon or list of authentic books of the Bible. Ruhnken had a kind of secular catechism in mind.