We naturally think first of the direct statements made by Latin writers. These are to be found in the writings of Cicero, Quintilian, Seneca the Rhetorician, Petronius, Aulus Gellius, Vitruvius, and the Latin grammarians. The professional teacher Quintilian is shocked at the illiterate speech of the spectators in the theatres and circus. Similarly a character in Petronius utters a warning against the words such people use. Cicero openly delights in using every-day Latin in his familiar letters, while the architect Vitruvius expresses the anxious fear that he may not be following the accepted rules of grammar. As we have noticed above, a great deal of material showing the differences between formal and colloquial Latin which these writers have in mind, may be obtained by comparing, for instance, the Letters of Cicero with his rhetorical works, or Seneca's satirical skit on the Emperor Claudius with his philosophical writings. Now and then, too, a serious writer has occasion to use a bit of popular Latin, but he conveniently labels it for us with an apologetic phrase. Thus even St. Jerome, in his commentary on the Epistle to the Ephesians, says: "Don't look a gift horse in the mouth, as the vulgar proverb has it." To the ancient grammarians the "mistakes" and vulgarisms of popular speech were abhorrent, and they have fortunately branded lists of words and expressions which are not to be used by cultivated people. The evidence which may be had from the Romance languages, supplemented by Latin, not only contributes to our knowledge of the vocabulary of vulgar Latin, but it also shows us many common idioms and constructions which that form of speech had. Thus, "I will sing" in Italian is canterò (=cantar[e]-ho), in Spanish, cantaré (=cantar-he), in French, chanterai (=chanter-ai), and similar forms occur in some of the other Romance languages. These forms are evidently made up of the Latin infinitive cantare, depending on habeo ("I have to sing"). But the future in literary Latin was cantabo, formed by adding an ending, as we know, and with that the Romance future can have no connection. However, as a writer in the Archiv has pointed out, just such analytical tense forms as are used in the Romance languages to-day are to be found in the popular Latin sermons of St. Jerome. From these idioms, common to Italian, French, and Spanish, then, we can reconstruct a Latin formation current among the common people. Finally a knowledge of the tendencies and practices of spoken English helps us to identify similar usages when we come upon them in our reading of Latin. When, for instance, the slave in a play of Plautus says: "Do you catch on" (tenes?), "I'll touch the old man for a loan" (tangam senem, etc.), or "I put it over him" (ei os sublevi) we recognize specimens of Latin slang, because all of the metaphors involved are in current use to-day. When one of the freedmen in Petronius remarks: "You ought not to do a good turn to nobody" (neminem nihil boni facere oportet) we see the same use of the double negative to which we are accustomed in illiterate English. The rapid survey which we have just made of the evidence bearing on the subject establishes beyond doubt the existence of a form of speech among the Romans which cannot be identified with literary Latin, but it has been held by some writers that the material for the study of it is scanty. However, an impartial examination of the facts ought not to lead one to this conclusion. On the Latin side the material includes the comedies of Plautus and Terence, and the comic fragments, the familiar odes of Catullus, the satires of Lucilius, Horace, and Seneca, and here and there of Persius and Juvenal, the familiar letters of Cicero, the romance of Petronius and that of Apuleius in part, the Vulgate and some of the Christian fathers, the Journey to Jerusalem of St. Ætheria, the glossaries, some technical books like Vitruvius and the veterinary treatise of Chiron, and the private inscriptions, notably epitaphs, the wall inscriptions of Pompeii, and the leaden tablets found buried in the ground on which illiterate people wrote curses upon their enemies.
It is clear that there has been preserved for the study of colloquial Latin a very large body of material, coming from a great variety of sources and running in point of time from Plautus in the third century B.C. to St. Ætheria in the latter part of the fourth century or later. It includes books by trained writers, like Horace and Petronius, who consciously adopt the Latin of every-day life, and productions by uneducated people, like St. Ætheria and the writers of epitaphs, who have unwittingly used it.
St. Jerome says somewhere of spoken Latin that "it changes constantly as you pass from one district to another, and from one period to another" (et ipsa Latinitas et regionibus cotidie mutatur et tempore). If he had added that it varies with circumstances also, he would have included the three factors which have most to do in influencing the development of any spoken language. We are made aware of the changes which time has brought about in colloquial English when we compare the conversations in Fielding with those in a present-day novel. When a spoken language is judged by the standard of the corresponding literary medium, in some of its aspects it proves to be conservative, in others progressive. It shows its conservative tendency by retaining many words and phrases which have passed out of literary use. The English of the Biglow Papers, when compared with the literary speech of the time, abundantly illustrates this fact. This conservative tendency is especially noticeable in districts remote from literary centres, and those of us who are familiar with the vernacular in Vermont or Maine will recall in it many quaint words and expressions which literature abandoned long ago. In Virginia locutions may be heard which have scarcely been current in literature since Shakespeare's time. Now, literary and colloquial Latin were probably drawn farther apart than the two corresponding forms of speech in English, because Latin writers tried to make the literary tongue as much like Greek in its form as possible, so that literary Latin would naturally have diverged more rapidly and more widely from conversational Latin than formal English has drawn away from colloquial English.
But a spoken language in its development is progressive as well as conservative. To certain modifying influences it is especially sensitive. It is fond of the concrete, picturesque, and novel, and has a high appreciation of humor. These tendencies lead it to invent many new words and expressions which must wait months, years, perhaps a generation, before they are accepted in literature. Sometimes they are never accepted. The history of such words as buncombe, dude, Mugwump, gerrymander, and joy-ride illustrate for English the fact that words of a certain kind meet a more hospitable reception in the spoken language than they do in literature. The writer of comedy or farce, the humorist, and the man in the street do not feel the constraint which the canons of good usage put on the serious writer. They coin new words or use old words in a new way or use new constructions without much hesitation. The extraordinary material progress of the modern world during the last century has undoubtedly stimulated this tendency in a remarkable way, but it would seem as if the Latin of the common people from the time of Plautus to that of Cicero must have been subjected to still more innovating influences than modern conversational English has. During this period the newly conquered territories in Spain, northern Africa, Greece, and Asia poured their slaves and traders into Italy, and added a great many words to the vocabulary of every-day life. The large admixture of Greek words and idioms in the language of Petronius in the first century of our era furnishes proof of this fact. A still greater influence must have been felt within the language itself by the stimulus to the imagination which the coming of these foreigners brought, with their new ideas, and their new ways of looking at things, their strange costumes, manners, and religions.
The second important factor which affects the spoken language is a difference in culture and training. The speech of the gentleman differs from that of the rustic. The conversational language of Terence, for instance, is on a higher plane than that of Plautus, while the characters in Plautus use better Latin than the freedmen in Petronius. The illiterate freedmen in Petronius speak very differently from the freemen in his story. Sometimes a particular occupation materially affects the speech of those who pursue it. All of us know something of the linguistic eccentricities of the London cabman, the Parisian thief, or the American hobo. This particular influence cannot be estimated so well for Latin because we lack sufficient material, but some progress has been made in detecting the peculiarities of Latin of the nursery, the camp, and the sea.
Of course a spoken language is never uniform throughout a given area. Dialectal differences are sure to develop. A man from Indiana and another from Maine will be sure to notice each other's peculiarities. Even the railway, the newspaper, and the public school will never entirely obliterate the old differences or prevent new ones from springing up. Without these agencies which do so much to promote uniformity to-day, Italy and the rest of the Empire must have shown greater dialectal differences than we observe in American English or in British English even.
For the sake of bringing out clearly some of the points of difference between vulgar and formal Latin we have used certain illustrations, like caballus, where the two forms of speech were radically opposed to each other, but of course they did not constitute two different languages, and that which they had in common was far greater than the element peculiar to each, or, to put it in another way, they in large measure overlapped each other. Perhaps we are in a position now to characterize colloquial Latin and to define it as the language which was used in conversation throughout the Empire with the innumerable variations which time and place gave it, which in its most highly refined form, as spoken in literary circles at Rome in the classical period, approached indefinitely near its ideal, literary Latin, which in its most unconventional phase was the rude speech of the rabble, or the "sermo inconditus" of the ancients. The facts which have just been mentioned may be illustrated by the accompanying diagrams.
In Fig. I the heavy-lined ellipse represents the formal diction of Cicero, the dotted line ellipse his conversational vocabulary. They overlap each other through a great part of their extent, but there are certain literary locutions which would rarely be used by him in conversation, and certain colloquial words and phrases which he would not use in formal writing. Therefore the two ellipses would not be coterminous. In Fig. II the heavy ellipse has the same meaning as in Fig. I, while the space enclosed by the dotted line represents the vocabulary of an uneducated Roman, which would be much smaller than that of Cicero and would show a greater degree of difference from the literary vocabulary than Cicero's conversational stock of words does. The relation of the uncultivated Roman's conversational vocabulary to that of Cicero is illustrated in Fig. III, while Fig. IV shows how the Latin of the average man in Rome would compare, for instance, with that of a resident of Lugudunum, in Gaul.