The great number of definitions proposed for the term Vulgar Latin mirrors the plurality of Vulgar Latin theories, which cannot all be correct. They not only do not all coincide, which is but natural, but some of them are radically opposed to each other. Since all of them are based on the same records, the divergence of theories must spring from the interpretation and not from the nature of the evidence.
One may completely discard, as the majority of scholars have done, the idea that spoken Vulgar Latin is the chronological successor (a corruption) of Classical Latin. Apart from this antiquated view, there are, roughly, two types of Vulgar Latin theories. First, there are theories which propose that there was, especially during the Empire and the early Middle Ages, a linguistic unity of popular speech throughout the Roman and Romanized world; according to some scholars this unity dissolved in the 5th or 6th century of our era, according to others not before the end of the 8th or 9th century. Second, there are theories which insist on early dialectalization of Latin, or indeed maintain that there never was, outside of early Latium, a single unified Latin, or anything but a number of local dialects, especially in the Romania outside of Italy.