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.

[Illustration:  Fig.  I]

[Illustration:  Fig.  II]

[Illustration:  Fig.  III]

[Illustration:  Fig.  IV]