 Finally, it should be pointed out that doxographic works are tools of a sort. They constitute a type of secondary literature of a fluid and unstable character, both as to form and as to contents. Shorter and longer versions may be available alongside each other; in fact, for all the losses sustained by ancient literature, some still are. Materials may be added, or lost, or added again in a continuous process of epitomizing and enlarging and updating—and it remained possible, of course, to inspect and excerpt original sources at least in some cases. 