 In the Middle Ages, as in other periods, philosophy took many written forms, from encyclopaedias and compendia to monographs and short essays, from poetic, allegorical, and novelistic presentations to texts based directly on school and university practice (such as quodlibets) (see entry on  Literary Forms of Medieval Philosophy).  But there is one literary form that was used centrally in all the four traditions, but has lost its importance in modern times: the commentary. Much of the best medieval philosophy was done in commentaries, many of which were far from mere aids to understanding the text concerned. Whereas philosophers now, at least in the analytic tradition, think of their subject as made up of problems, which are tackled using what others have said and are saying as aids, medieval philosophizing was frequently based on (often, but not always, old and venerated) texts. But, although the aim was usually to interpret them, the practice of interpretation frequently led to new thinking, related only tangentially to the text under discussion.