The one-volume Propædia is the first of three parts of the 15th edition of Encyclopædia Britannica, intended as a compendium and topical organization of the 12-volume Micropædia and the 17-volume Macropædia, which are organized alphabetically. Introduced in 1974 with the 15th edition, the Propædia and Micropædia were intended to replace the Index of the 14th edition; however, after widespread criticism, the Britannica restored the Index as a two-volume set in 1985. The core of the Propædia is its Outline of Knowledge, which seeks to provide a logical framework for all human knowledge. However, the Propædia also has several appendices listing the staff members, advisors and contributors to all three parts of the Britannica.